Enforce and advertise the method enum for method-dispatch tools

The consolidated method-dispatch tools returned a bare "unknown method: <x>"
with no hint of valid values, and each tool's valid method set lived only in
its schema enum (or, for sub_issue_write, only in prose). labels.go already
listed the supported methods on an unknown value; this brings the rest in line
and makes the advertised methods the single source of truth.

- Each tool's method set is a single []string that feeds both the input-schema
  enum (methodEnum) and the unknown-method error (unknownMethodError), so the
  advertised methods and the accepted methods cannot drift apart.
- An unknown method now lists the supported set:
  "unknown method: x. Supported methods are: ...".
- pull_request_review_write decoded args with WeakDecode (no RequiredParam), so
  an omitted method surfaced as "unknown method: " (empty). It now reports
  "missing required parameter: method", consistent with the other tools.
- sub_issue_write advertised its method options only in the description; it now
  declares the enum like every other method-dispatch tool.

Closes #2712

Author: gustavo-sec

pkg/github/__toolsnaps__/sub_issue_write.snap

@@ -19,6 +19,11 @@
       },
       "method": {
         "description": "The action to perform on a single sub-issue\nOptions are:\n- 'add' - add a sub-issue to a parent issue in a GitHub repository.\n- 'remove' - remove a sub-issue from a parent issue in a GitHub repository.\n- 'reprioritize' - change the order of sub-issues within a parent issue in a GitHub repository. Use either 'after_id' or 'before_id' to specify the new position.\n\t\t\t\t",
+        "enum": [
+          "add",
+          "remove",
+          "reprioritize"
+        ],
         "type": "string"
       },
       "owner": {

pkg/github/actions.go

@@ -46,6 +46,15 @@ const (
 	actionsMethodDeleteWorkflowRunLogs    = "delete_workflow_run_logs"
 )
 
+// Method sets for the consolidated actions tools. Each slice is the single
+// source for its tool: it feeds both the schema enum (methodEnum) and the
+// unknown-method error (unknownMethodError). Order matches the advertised enum.
+var (
+	actionsWorkflowListMethods = []string{actionsMethodListWorkflows, actionsMethodListWorkflowRuns, actionsMethodListWorkflowJobs, actionsMethodListWorkflowArtifacts}
+	actionsWorkflowGetMethods  = []string{actionsMethodGetWorkflow, actionsMethodGetWorkflowRun, actionsMethodGetWorkflowJob, actionsMethodDownloadWorkflowArtifact, actionsMethodGetWorkflowRunUsage, actionsMethodGetWorkflowRunLogsURL}
+	actionsWorkflowRunMethods  = []string{actionsMethodRunWorkflow, actionsMethodRerunWorkflowRun, actionsMethodRerunFailedJobs, actionsMethodCancelWorkflowRun, actionsMethodDeleteWorkflowRunLogs}
+)
+
 // handleFailedJobLogs gets logs for all failed jobs in a workflow run
 func handleFailedJobLogs(ctx context.Context, client *github.Client, owner, repo string, runID int64, returnContent bool, tailLines int, contentWindowSize int) (*mcp.CallToolResult, any, error) {
 	// First, get all jobs for the workflow run
@@ -217,12 +226,7 @@ Use this tool to list workflows in a repository, or list workflow runs, jobs, an
 					"method": {
 						Type:        "string",
 						Description: "The action to perform",
-						Enum: []any{
-							actionsMethodListWorkflows,
-							actionsMethodListWorkflowRuns,
-							actionsMethodListWorkflowJobs,
-							actionsMethodListWorkflowArtifacts,
-						},
+						Enum:        methodEnum(actionsWorkflowListMethods),
 					},
 					"owner": {
 						Type:        "string",
@@ -397,7 +401,7 @@ Use this tool to list workflows in a repository, or list workflow runs, jobs, an
 				result, payload, err := listWorkflowArtifacts(ctx, client, owner, repo, resourceIDInt, pagination)
 				return attachIFC(result), payload, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, actionsWorkflowListMethods), nil, nil
 			}
 		},
 	)
@@ -423,14 +427,7 @@ Use this tool to get details about individual workflows, workflow runs, jobs, an
 					"method": {
 						Type:        "string",
 						Description: "The method to execute",
-						Enum: []any{
-							actionsMethodGetWorkflow,
-							actionsMethodGetWorkflowRun,
-							actionsMethodGetWorkflowJob,
-							actionsMethodDownloadWorkflowArtifact,
-							actionsMethodGetWorkflowRunUsage,
-							actionsMethodGetWorkflowRunLogsURL,
-						},
+						Enum:        methodEnum(actionsWorkflowGetMethods),
 					},
 					"owner": {
 						Type:        "string",
@@ -519,7 +516,7 @@ Use this tool to get details about individual workflows, workflow runs, jobs, an
 				result, payload, err := getWorkflowRunLogsURL(ctx, client, owner, repo, resourceIDInt)
 				return attachIFC(result), payload, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, actionsWorkflowGetMethods), nil, nil
 			}
 		},
 	)
@@ -544,13 +541,7 @@ func ActionsRunTrigger(t translations.TranslationHelperFunc) inventory.ServerToo
 					"method": {
 						Type:        "string",
 						Description: "The method to execute",
-						Enum: []any{
-							actionsMethodRunWorkflow,
-							actionsMethodRerunWorkflowRun,
-							actionsMethodRerunFailedJobs,
-							actionsMethodCancelWorkflowRun,
-							actionsMethodDeleteWorkflowRunLogs,
-						},
+						Enum:        methodEnum(actionsWorkflowRunMethods),
 					},
 					"owner": {
 						Type:        "string",
@@ -636,7 +627,7 @@ func ActionsRunTrigger(t translations.TranslationHelperFunc) inventory.ServerToo
 			case actionsMethodDeleteWorkflowRunLogs:
 				return deleteWorkflowRunLogs(ctx, client, owner, repo, int64(runID))
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, actionsWorkflowRunMethods), nil, nil
 			}
 		},
 	)

pkg/github/issues.go

@@ -24,6 +24,13 @@ import (
 	"github.com/shurcooL/githubv4"
 )
 
+// Method sets for the consolidated issue tools (single source for the schema
+// enum via methodEnum and the unknown-method error via unknownMethodError).
+var (
+	issueReadMethods     = []string{"get", "get_comments", "get_sub_issues", "get_labels"}
+	subIssueWriteMethods = []string{"add", "remove", "reprioritize"}
+)
+
 // CloseIssueInput represents the input for closing an issue via the GraphQL API.
 // Used to extend the functionality of the githubv4 library to support closing issues as duplicates.
 type CloseIssueInput struct {
@@ -736,7 +743,7 @@ Options are:
 3. get_sub_issues - Get sub-issues of the issue.
 4. get_labels - Get labels assigned to the issue.
 `,
-				Enum: []any{"get", "get_comments", "get_sub_issues", "get_labels"},
+				Enum: methodEnum(issueReadMethods),
 			},
 			"owner": {
 				Type:        "string",
@@ -820,7 +827,7 @@ Options are:
 				result, err := GetIssueLabels(ctx, gqlClient, owner, repo, issueNumber)
 				return attachIFC(result), nil, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, issueReadMethods), nil, nil
 			}
 		})
 }
@@ -1234,6 +1241,7 @@ func SubIssueWrite(t translations.TranslationHelperFunc) inventory.ServerTool {
 				Properties: map[string]*jsonschema.Schema{
 					"method": {
 						Type: "string",
+						Enum: methodEnum(subIssueWriteMethods),
 						Description: `The action to perform on a single sub-issue
 Options are:
 - 'add' - add a sub-issue to a parent issue in a GitHub repository.
@@ -1327,7 +1335,7 @@ Options are:
 				result, err := ReprioritizeSubIssue(ctx, client, owner, repo, issueNumber, subIssueID, afterID, beforeID)
 				return result, nil, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, subIssueWriteMethods), nil, nil
 			}
 		})
 	st.FeatureFlagDisable = []string{FeatureFlagIssuesGranular}

pkg/github/params.go

@@ -5,9 +5,12 @@ import (
 	"fmt"
 	"math"
 	"strconv"
+	"strings"
 
+	"github.com/github/github-mcp-server/pkg/utils"
 	"github.com/google/go-github/v87/github"
 	"github.com/google/jsonschema-go/jsonschema"
+	"github.com/modelcontextprotocol/go-sdk/mcp"
 )
 
 // OptionalParamOK is a helper function that can be used to fetch a requested parameter from the request.
@@ -488,3 +491,23 @@ func (p PaginationParams) ToGraphQLParams() (*GraphQLPaginationParams, error) {
 	}
 	return cursor.ToGraphQLParams()
 }
+
+// methodEnum renders a tool's supported method list as the []any value the
+// input-schema Enum field expects. Declaring the enum from the same []string
+// the handler validates against keeps the advertised methods and the runtime
+// check from drifting apart.
+func methodEnum(methods []string) []any {
+	out := make([]any, len(methods))
+	for i, m := range methods {
+		out[i] = m
+	}
+	return out
+}
+
+// unknownMethodError is the tool-result error returned when a method-dispatch
+// tool is called with a value outside its advertised method enum. Listing the
+// supported methods lets the caller (often an LLM) self-correct. supported must
+// be the same list advertised in the tool's input-schema enum.
+func unknownMethodError(method string, supported []string) *mcp.CallToolResult {
+	return utils.NewToolResultError(fmt.Sprintf("unknown method: %s. Supported methods are: %s", method, strings.Join(supported, ", ")))
+}

pkg/github/params_test.go

@@ -642,3 +642,19 @@ func TestOptionalPaginationParams(t *testing.T) {
 		})
 	}
 }
+
+func TestMethodEnum(t *testing.T) {
+	// methodEnum must preserve methods and order so the advertised schema enum
+	// stays byte-identical to the source slice.
+	assert.Equal(t, []any{"create", "submit_pending"}, methodEnum([]string{"create", "submit_pending"}))
+	assert.Empty(t, methodEnum(nil))
+}
+
+func TestUnknownMethodError(t *testing.T) {
+	res := unknownMethodError("bogus", []string{"create", "submit_pending", "delete_pending"})
+	assert.NotNil(t, res)
+	assert.True(t, res.IsError)
+	txt := getErrorResult(t, res).Text
+	assert.Contains(t, txt, "unknown method: bogus")
+	assert.Contains(t, txt, "Supported methods are: create, submit_pending, delete_pending")
+}

pkg/github/projects.go

@@ -51,6 +51,15 @@ const (
 	projectsMethodCreateIterationField      = "create_iteration_field"
 )
 
+// Method sets for the consolidated project tools. Single source per tool: feeds
+// both the schema enum (methodEnum) and the unknown-method error
+// (unknownMethodError). Order matches the advertised enum.
+var (
+	projectsListMethods  = []string{projectsMethodListProjects, projectsMethodListProjectFields, projectsMethodListProjectItems, projectsMethodListProjectStatusUpdates}
+	projectsGetMethods   = []string{projectsMethodGetProject, projectsMethodGetProjectField, projectsMethodGetProjectItem, projectsMethodGetProjectStatusUpdate}
+	projectsWriteMethods = []string{projectsMethodAddProjectItem, projectsMethodUpdateProjectItem, projectsMethodDeleteProjectItem, projectsMethodCreateProjectStatusUpdate, projectsMethodCreateProject, projectsMethodCreateIterationField}
+)
+
 // GraphQL types for ProjectV2 status updates
 
 type statusUpdateNode struct {
@@ -159,12 +168,7 @@ Use this tool to list projects for a user or organization, or list project field
 					"method": {
 						Type:        "string",
 						Description: "The action to perform",
-						Enum: []any{
-							projectsMethodListProjects,
-							projectsMethodListProjectFields,
-							projectsMethodListProjectItems,
-							projectsMethodListProjectStatusUpdates,
-						},
+						Enum:        methodEnum(projectsListMethods),
 					},
 					"owner_type": {
 						Type:        "string",
@@ -269,7 +273,7 @@ Use this tool to list projects for a user or organization, or list project field
 					result, payload, err := listProjectStatusUpdates(ctx, gqlClient, args, owner, ownerType)
 					return attachIFC(result), payload, err
 				default:
-					return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+					return unknownMethodError(method, projectsListMethods), nil, nil
 				}
 			}
 		},
@@ -296,12 +300,7 @@ Use this tool to get details about individual projects, project fields, and proj
 					"method": {
 						Type:        "string",
 						Description: "The method to execute",
-						Enum: []any{
-							projectsMethodGetProject,
-							projectsMethodGetProjectField,
-							projectsMethodGetProjectItem,
-							projectsMethodGetProjectStatusUpdate,
-						},
+						Enum:        methodEnum(projectsGetMethods),
 					},
 					"owner_type": {
 						Type:        "string",
@@ -419,7 +418,7 @@ Use this tool to get details about individual projects, project fields, and proj
 				result, payload, err := getProjectItem(ctx, client, owner, ownerType, projectNumber, itemID, fields)
 				return attachIFC(result), payload, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, projectsGetMethods), nil, nil
 			}
 		},
 	)
@@ -444,14 +443,7 @@ func ProjectsWrite(t translations.TranslationHelperFunc) inventory.ServerTool {
 					"method": {
 						Type:        "string",
 						Description: "The method to execute",
-						Enum: []any{
-							projectsMethodAddProjectItem,
-							projectsMethodUpdateProjectItem,
-							projectsMethodDeleteProjectItem,
-							projectsMethodCreateProjectStatusUpdate,
-							projectsMethodCreateProject,
-							projectsMethodCreateIterationField,
-						},
+						Enum:        methodEnum(projectsWriteMethods),
 					},
 					"owner_type": {
 						Type:        "string",
@@ -669,7 +661,7 @@ func ProjectsWrite(t translations.TranslationHelperFunc) inventory.ServerTool {
 			case projectsMethodCreateIterationField:
 				return createIterationField(ctx, gqlClient, owner, ownerType, projectNumber, args)
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, projectsWriteMethods), nil, nil
 			}
 		},
 	)

pkg/github/projects_test.go

@@ -93,7 +93,7 @@ func Test_ProjectsList_ListProjects(t *testing.T) {
 				"owner_type": "org",
 			},
 			expectError:    true,
-			expectedErrMsg: "unknown method: unknown_method",
+			expectedErrMsg: "unknown method: unknown_method. Supported methods are:",
 		},
 	}
 
@@ -435,6 +435,7 @@ func Test_ProjectsGet_GetProject(t *testing.T) {
 		require.True(t, result.IsError)
 		textContent := getTextResult(t, result)
 		assert.Contains(t, textContent.Text, "unknown method: unknown_method")
+		assert.Contains(t, textContent.Text, "Supported methods are:")
 	})
 }
 
@@ -850,6 +851,7 @@ func Test_ProjectsWrite_AddProjectItem(t *testing.T) {
 		require.True(t, result.IsError)
 		textContent := getTextResult(t, result)
 		assert.Contains(t, textContent.Text, "unknown method: unknown_method")
+		assert.Contains(t, textContent.Text, "Supported methods are:")
 	})
 }
 

pkg/github/pullrequests.go

@@ -23,6 +23,13 @@ import (
 	"github.com/github/github-mcp-server/pkg/utils"
 )
 
+// Method sets for the consolidated pull request tools (single source for the
+// schema enum via methodEnum and the unknown-method error via unknownMethodError).
+var (
+	pullRequestReadMethods        = []string{"get", "get_diff", "get_status", "get_files", "get_commits", "get_review_comments", "get_reviews", "get_comments", "get_check_runs"}
+	pullRequestReviewWriteMethods = []string{"create", "submit_pending", "delete_pending", "resolve_thread", "unresolve_thread"}
+)
+
 // PullRequestRead creates a tool to get details of a specific pull request.
 func PullRequestRead(t translations.TranslationHelperFunc) inventory.ServerTool {
 	schema := &jsonschema.Schema{
@@ -42,7 +49,7 @@ Possible options:
  8. get_comments - Get comments on a pull request. Use this if user doesn't specifically want review comments. Use with pagination parameters to control the number of results returned.
  9. get_check_runs - Get check runs for the head commit of a pull request. Check runs are the individual CI/CD jobs and checks that run on the PR.
 `,
-				Enum: []any{"get", "get_diff", "get_status", "get_files", "get_commits", "get_review_comments", "get_reviews", "get_comments", "get_check_runs"},
+				Enum: methodEnum(pullRequestReadMethods),
 			},
 			"owner": {
 				Type:        "string",
@@ -155,7 +162,7 @@ Possible options:
 				result, err := GetPullRequestCheckRuns(ctx, client, owner, repo, pullNumber, pagination)
 				return attachIFC(result), nil, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", method)), nil, nil
+				return unknownMethodError(method, pullRequestReadMethods), nil, nil
 			}
 		})
 }
@@ -1728,7 +1735,7 @@ func PullRequestReviewWrite(t translations.TranslationHelperFunc) inventory.Serv
 			"method": {
 				Type:        "string",
 				Description: `The write operation to perform on pull request review.`,
-				Enum:        []any{"create", "submit_pending", "delete_pending", "resolve_thread", "unresolve_thread"},
+				Enum:        methodEnum(pullRequestReviewWriteMethods),
 			},
 			"owner": {
 				Type:        "string",
@@ -1789,6 +1796,15 @@ Available methods:
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
 
+			// Unlike the other method-dispatch tools, this handler decodes args
+			// with WeakDecode rather than RequiredParam, so an omitted method
+			// would otherwise reach the switch default as an empty value. Enforce
+			// it explicitly so a missing method is reported the same way as every
+			// other missing required parameter.
+			if _, err := RequiredParam[string](args, "method"); err != nil {
+				return utils.NewToolResultError(err.Error()), nil, nil
+			}
+
 			// Given our owner, repo and PR number, lookup the GQL ID of the PR.
 			client, err := deps.GetGQLClient(ctx)
 			if err != nil {
@@ -1812,7 +1828,7 @@ Available methods:
 				result, err := ResolveReviewThread(ctx, client, params.ThreadID, false)
 				return result, nil, err
 			default:
-				return utils.NewToolResultError(fmt.Sprintf("unknown method: %s", params.Method)), nil, nil
+				return unknownMethodError(params.Method, pullRequestReviewWriteMethods), nil, nil
 			}
 		})
 	st.FeatureFlagDisable = []string{FeatureFlagPullRequestsGranular}