feat(server): advertise outputSchema on tools/list (JS parity)

[bokelley]

Context

tools/list advertises only inputSchema per tool. ADCP_TOOL_DEFINITIONS in src/adcp/server/mcp_tools.py does not include outputSchema. FastMCP knows the output schemas internally — it uses them to populate structuredContent in serve.py:1427 — but they are not published on tools/list. The TS SDK advertises both inputSchema and outputSchema.

Refs:

• src/adcp/server/mcp_tools.py (ADCP_TOOL_DEFINITIONS)
• src/adcp/server/serve.py:1427 (where FastMCP uses output schemas internally)

Acceptance Criteria

• Add outputSchema per tool in ADCP_TOOL_DEFINITIONS (or generate it from the same source FastMCP uses internally — single source of truth)
• tools/list response carries both inputSchema and outputSchema
• Schemas validate against the AdCP response schemas in CI
• Smoke test: every advertised tool can have its declared outputSchema validate against the actual response from a no-op invocation
• CHANGELOG note: matches TS SDK tools/list shape

[bokelley]

Triage

Classification: Feature request
Bucket(s): handlers, client
Status: drafting-pr
Milestone: (omitted — no target version specified)

What the experts said:

• ad-tech-protocol-expert: outputSchema ratified in MCP spec 2025-03-26; anyOf for union responses is canonical; non-enforcement of structuredContent at runtime is acceptable per §5.4.3
• code-reviewer: approach is sound; _tool_to_response mapping mirrors existing _tool_to_request pattern; drift tests cover all failure modes

My take: Non-breaking additive change — MCP clients that don't understand outputSchema ignore it. The Pydantic response types already exist for every tool; the machinery to generate and inline schemas mirrors the existing inputSchema path exactly.

Drafting PR: add outputSchema to every entry in ADCP_TOOL_DEFINITIONS from Pydantic response models; thread through _register_tool to patch fn_metadata.output_schema for tools/list advertisement while keeping the generic output_model for runtime structuredContent.

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Triaged by Claude Code. Session: https://claude.ai/code/session_019UpkNNacQ4QS8zcVTRfFQV

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Generated by Claude Code