Feature Request: session-scoped tool inventory API (list MCP-discovered tools loaded into a session)

まず createSessionRpc の実装と、既存の session.rpc.{mcp,skills,plugins,extensions}.list() ラッパーを読みます。Python、Go、.NET のパリティ要件について CONTRIBUTING を確認し、サーバー側の RPC ハンドラーがこのリポジトリの外部にある場合でも api.schema.json を確認します。内部 RPC が利用可能になることを前提として、サポート対象の SDK バインディングが一貫したセッションスコープの tools.list 結果を公開できれば完了です。

Problem

No public API enumerates the tools loaded into a session — built-ins merged with MCP-discovered tools from SessionConfig.mcpServers. Closest existing surfaces don't cover it:

• client.rpc.tools.list({ model? }) is server-scoped — built-ins only, no session-loaded MCP tools.
• session.rpc.mcp.list() returns server connection status (name, status, error?, source?), not tools or counts per server.
• session.mcp_servers_loaded event fires once on session startup but carries the same server-status-only payload — no tool list.
• session.mcp_server_status_changed carries { serverName, status } only.
• session.tools_updated event payload is just { model: string }.

A session can report mcp.status: "connected" and still expose zero tools (wrong CLI flags, version mismatch, schema error) — there's no SDK-side way to detect this.

Why it's needed

• Operational visibility. Confirm before the first turn that an MCP server actually contributed the expected tools, not just that its process started.
• Diagnostic UIs. Surface per-server tool counts to operators of BYOK / multi-MCP deployments.
• Test assertions. Verify a given MCP wiring exposes the expected tool set without spawning a parallel tools/list probe.
• Parity with prior MCP clients. Other MCP integrations (e.g. @ai-sdk/mcp) expose discovered tools as an enumerable map; consumers migrating to copilot-sdk lose this.

Contribution scope

api.schema.json ships from the closed @github/copilot npm package (the public github/copilot-cli repo is just the installer). The server-side RPC handler must live in the internal CLI — external contributors can only touch SDK bindings/wrappers in this repo, not the underlying RPC implementation.

Proposed solution

Add a session-scoped tools.list RPC, mirroring the existing client.rpc.tools.list() but reflecting per-session config:

// in createSessionRpc:
tools: {
  list: async (): Promise<SessionToolsListResult> =>
    connection.sendRequest("session.tools.list", { sessionId }),
  handlePendingToolCall: /* unchanged */,
}

export interface SessionToolsListResult {
  tools: Tool[]; // namespacedName populated for MCP tools (e.g. "playwright/browser_navigate")
}

Returns built-ins (post-excludedTools/availableTools filtering) + MCP-contributed tools. Consistent with existing session.rpc.{mcp,skills,plugins,extensions}.list() shape. Parity in Python/Go/.NET per CONTRIBUTING.

A leaner alternative: enrich McpServer with toolCount?: number and/or tools?: string[]. Less consistent with the existing pattern but lighter.

Related

• #944 — same underlying gap, surfaced as a question.
• #735 — adjacent (manipulating session tool set without teardown).

Environment

@github/copilot-sdk@0.3.0