feat: add per-agent skills support to SDK types and docs (#958)

[MackinnonBuck]

Summary

Adds SDK support for scoping skills to individual subagents, addressing #958.

Changes

Types (all 4 SDKs):

• Node.js (nodejs/src/types.ts): Added skills?: string[] to CustomAgentConfig
• Python (python/copilot/session.py): Added skills field to agent config
• Go (go/types.go): Added Skills []string to agent config struct
• .NET (dotnet/src/Types.cs): Added List<string>? Skills to agent config class

Documentation:

• docs/features/custom-agents.md: Added skills to config reference table and new section on per-agent skills
• docs/features/skills.md: Updated "Skills + Custom Agents" section with per-agent example
• docs/features/streaming-events.md: Added agentName field to skill.invoked event docs

Tests (all 4 SDKs):

• Node.js, Python, Go, .NET e2e tests covering:
  • Agent with skills can invoke listed skills
  • Agent without skills field gets no skills (backward compatible)

Design decisions

• Opt-in model: skills is optional. Omitting it means the agent has no access to skills (not all skills).
• Name-based resolution: Skills are referenced by name from the session-level skillDirectories pool.
• Cross-SDK parity: All 4 SDKs support the new field consistently.

Depends on: github/copilot-agent-runtime PR (runtime must land first for e2e tests to pass)

Closes #958

[Copilot]

Pull request overview

Adds per-custom-agent skill scoping to the SDK surface area (types + docs) and introduces new cross-SDK E2E coverage + replay snapshots for the opt-in behavior.

Changes:

• Added skills to CustomAgentConfig across Node.js, Python, Go, and .NET SDK types.
• Updated docs to describe per-agent skill scoping and added agentName to skill.invoked event docs.
• Added E2E tests and new replay snapshots for “agent with skills” vs “agent without skills field”.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
nodejs/src/types.ts	Adds skills?: string[] to CustomAgentConfig with JSdoc explaining opt-in semantics.
python/copilot/session.py	Adds skills to the Python CustomAgentConfig TypedDict.
go/types.go	Adds Skills []string to Go CustomAgentConfig for JSON serialization.
dotnet/src/Types.cs	Adds List<string>? Skills to .NET CustomAgentConfig with XML docs.
docs/features/custom-agents.md	Documents the new skills field and adds a dedicated per-agent skills section.
docs/features/skills.md	Updates “Skills + Custom Agents” section with per-agent skills example and opt-in note.
docs/features/streaming-events.md	Documents agentName on skill.invoked.
nodejs/test/e2e/skills.test.ts	Adds Node E2E tests for agent-scoped skills behavior.
python/e2e/test_skills.py	Adds Python E2E tests for agent-scoped skills behavior.
go/internal/e2e/skills_test.go	Adds Go E2E tests for agent-scoped skills behavior.
dotnet/test/SkillsTests.cs	Adds .NET E2E tests for agent-scoped skills behavior.
test/snapshots/skills/should_allow_agent_with_skills_to_invoke_skill.yaml	Replay snapshot for the “agent with skills can invoke” scenario.
test/snapshots/skills/should_not_provide_skills_to_agent_without_skills_field.yaml	Replay snapshot for the “no skills field => no skills” scenario.
nodejs/package-lock.json	Lockfile metadata updates.

Files not reviewed (1)

• nodejs/package-lock.json: Language not supported

[github-actions]

Generated by SDK Consistency Review Agent for issue #995

[github-actions]

Cross-SDK Consistency Review ✅

This PR maintains excellent cross-SDK consistency for the new skills field on CustomAgentConfig. All four implementations are present and parallel:

SDK	Type	Field
Node.js	types.ts	skills?: string[]
Python	session.py	skills: NotRequired[list[str]]
Go	types.go	Skills []string \json:"skills,omitempty"``
.NET	Types.cs	public List<string>? Skills { get; set; }

All four SDKs also have matching E2E tests with the same two scenarios:

• Agent with skills receives preloaded skill content ✅
• Agent without skills receives no skill content (opt-in model) ✅

Python's client.py correctly wires the new field through _convert_custom_agent_to_wire_format, consistent with how other optional fields (mcp_servers, infer) are handled.

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Minor note on PR description: The description lists docs/features/streaming-events.md as a changed file with "agentName field added to skill.invoked event docs", but this file is not in the actual diff and agentName does not appear in the current skill.invoked type definitions in any SDK. This looks like a stale entry in the PR description — worth cleaning up to avoid confusion, but it doesn't affect the implementation correctness.

Generated by SDK Consistency Review Agent for issue #995 · ◷