Safe-outputs: add schema-driven synonym mapping (incl. camelCase aliases), keep synonym metadata internal to MCP/CLI prompts, and enforce strict unknown-parameter errors; clarify schema constraints

[Copilot]

Safe-output runs were incurring avoidable schema rejections due to ambiguous parameter naming (level vs severity, commit_message vs message), undocumented size constraints, and noop payload shape confusion. This change adds schema-driven parameter synonym acceptance, keeps synonym metadata internal (not exposed to LLM-facing MCP/CLI schemas), and upgrades strict-schema validation to reject unknown parameters with nearest valid-field suggestions.

• Argument normalization: schema-defined synonyms

  • Extended safe-output argument normalization to read per-field x-synonyms from inputSchema.properties and remap aliases to canonical fields before required-field validation.
  • Plumbed tool schema into the normalizer for both stdio and HTTP safe-output MCP server paths.
  • Expanded synonym coverage for likely LLM naming mistakes by adding camelCase aliases for snake_case parameters across safe-output schemas (for example, issueNumber → issue_number).

• Synonym metadata kept internal (no prompt pollution)

  • Added schema sanitization so internal correction metadata (for example x-synonyms) is stripped from MCP-exposed tool schemas (tools/list) and prompt-facing generation paths.
  • Preserved runtime synonym recovery by retaining original schemas internally for argument normalization.

• Strict unknown-parameter handling

  • Added strict-schema unknown-parameter detection (additionalProperties: false) in MCP core request handling.
  • Unknown keys now fail fast with explicit offending fields plus closest valid parameter suggestions and a bounded preview of supported parameters.

• Safe-output schema/docs disambiguation and constraints

  • Updated both schema copies (pkg/workflow/js/safe_outputs_tools.json and actions/setup/js/safe_outputs_tools.json) to:
    • clarify create_code_scanning_alert.severity (“NOT level”) and add x-synonyms: ["level"]
    • clarify push_to_pull_request_branch.message (“NOT commit_message”) and add x-synonyms: ["commit_message"]
    • clarify noop.message as the only content field and require serializing structured metrics into that string
    • document create_discussion.body max size (10 KB / 10240 bytes) with overflow guidance
  • Added/normalized synonym metadata where existing docs previously referenced stripped alternates (e.g., categoryId/category_id, issue_number).

• Focused regression coverage

  • Added tests for synonym remapping and for strict unknown-parameter rejection with closest-field suggestions.
  • Added regression coverage for camelCase alias remapping behavior.
  • Added regression coverage confirming synonym metadata is not exposed via MCP tools/list while synonym arguments are still accepted in tools/call.

// Example: schema-driven synonym remap + strict validation behavior
{
  inputSchema: {
    type: "object",
    additionalProperties: false,
    required: ["severity", "message"],
    properties: {
      severity: { type: "string", "x-synonyms": ["level"] },
      message: { type: "string" }
    }
  }
}

// call args: { level: "warning", message: "..." } -> normalized to { severity: "warning", message: "..." }
// call args: { sev: "warning", message: "..." }   -> rejected: unknown parameter 'sev' (closest: 'severity')
// tools/list output omits internal x-synonyms metadata

[pelikhan]

@copilot merge main, populate synonym with likely LLM mistakes

[Copilot]

@copilot merge main, populate synonym with likely LLM mistakes

Done in 3a27394 (merged main) and ddbd6a8 (expanded likely LLM synonym coverage with camelCase aliases across safe-output parameters, plus regression test update).

[pelikhan]

@copilot make sure the synonyms are not communicated to the LLM through the MCP or cli generation. They are internal correction data, but should not pollute the prompts.

[Copilot]

@copilot make sure the synonyms are not communicated to the LLM through the MCP or cli generation. They are internal correction data, but should not pollute the prompts.

Implemented in e7d29ba. x-synonyms now stays internal: safe-output tools still accept synonym arguments during normalization, but MCP-exposed schemas no longer include synonym metadata in tools/list.

[Copilot]

Pull request overview

This PR improves safe-outputs tool-call robustness by (1) normalizing tool arguments using schema-defined synonyms (including camelCase aliases), (2) stripping internal synonym metadata from MCP-exposed schemas, and (3) enforcing strict unknown-parameter rejection with “closest match” suggestions when schemas opt in via additionalProperties: false.

Changes:

• Add schema-driven synonym remapping (x-synonyms) to safe-output argument normalization, and plumb the tool input schema into the normalizer (stdio + HTTP servers).
• Sanitize tool schemas before exposing them via MCP (tools/list) by stripping x-synonyms, while retaining original schemas internally for runtime normalization.
• Add strict unknown-parameter validation in MCP core with nearest-valid-field suggestions and a bounded “supported parameters” preview; extend tests accordingly.

Show a summary per file

File	Description
pkg/workflow/js/safe_outputs_tools.json	Adds x-synonyms + doc clarifications to the safe-outputs tool schemas shipped with the workflow package.
actions/setup/js/safe_outputs_tools.json	Mirrors schema updates for the Actions setup copy (synonyms + doc clarifications).
actions/setup/js/safe_outputs_mcp_wrapped_arguments.test.cjs	Adds regression tests for synonym remapping and ensuring synonyms are not exposed via tools/list.
actions/setup/js/safe_outputs_mcp_server.cjs	Stores original schemas for normalization while stripping internal metadata from MCP-exposed schemas (stdio server).
actions/setup/js/safe_outputs_mcp_server_http.cjs	Same schema plumbing/sanitization as above for the HTTP server path.
actions/setup/js/safe_outputs_mcp_arguments.cjs	Implements synonym-based argument remapping and schema metadata stripping helper.
actions/setup/js/mcp_server_core.test.cjs	Adds coverage for strict unknown-parameter rejection + closest-parameter suggestions.
actions/setup/js/mcp_server_core.cjs	Implements unknown-parameter detection + error construction (gated by additionalProperties: false).

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• Files reviewed: 8/8 changed files
• Comments generated: 2