Tool Responses

Tool responses are product UX for agents and users. A response should help an assistant answer a real Sentry question without forcing it to understand upstream API shapes, internal implementation details, or placeholder values.

Use this policy when adding a tool, changing formatted handler output, updating snapshots, or QAing MCP behavior. For the full tool implementation flow, see adding-tools.md. For snapshot requirements, see ../testing/overview.md. For end-to-end MCP validation, see .agents/skills/mcp-qa/SKILL.md.

Response Contract

Every formatted tool response should optimize for:

• Usefulness: Include the fields someone needs to inspect, compare, explain, or act on the resource.
• Legibility: Use Sentry product terms and stable markdown sections.
• Actionability: Include IDs, URLs, pagination cursors, and follow-up tool hints only when they help navigation or the next tool call.
• Safety: Do not expose secrets, credentials, raw tokens, or unrelated internal details. Follow ../operations/security.md for security boundaries.
• Agent fit: The output should be easy for an LLM to quote, summarize, and reason over without post-processing raw API payloads.

Markdown Shape

Use a predictable markdown structure:

# Resource Type in **scope**

## Resource Name

**Kind**: Issue Alert
**ID**: 123
**Project**: backend
**Status**: enabled
**URL**: https://example.sentry.io/...

### Conditions

- Event frequency count (comparison: 10, result: true)

## Response Notes

- Use `get_alert_rule` with `kind` and the numeric rule ID for full details.

Guidelines:

• Start with a clear # title that names the resource set or detail scope.
• Use ## and ### sections for repeated resource groups and details.
• Prefer bold labels for scalar facts.
• Prefer bullets or compact tables for repeated items.
• Omit sections that have no meaningful data unless the absence itself matters.
• Use ## Response Notes only for scoped, result-specific guidance.

See common-patterns.md for shared schema and validation patterns used alongside response formatting.

Include

Include data that is useful for real user questions:

• Resource identity: name, kind, ID, org, project, slug, status.
• Navigation: web URLs, dashboard URLs, issue URLs, or monitor URLs.
• Operational state: owner, assignee, environment, release, last seen, last triggered, frequency, priority, or status.
• User-facing configuration: alert conditions, filters, triggers, actions, routing, notification targets, dashboard widgets, monitor schedules.
• Follow-up handles: IDs or cursors needed for a documented next tool call.
• Timestamps when they answer real freshness, history, or audit questions.

Avoid

Do not leak implementation details into ordinary tool output:

• Raw API JSON unless the tool explicitly returns raw data.
• Internal IDs that are not useful follow-up handles, such as workflow component IDs, detector IDs, synthetic filter IDs, or trace plumbing identifiers.
• Placeholder noise such as null, undefined, empty arrays, empty objects, empty strings, data:, or target display: unknown.
• Upstream field names when a user-facing label is obvious, such as conditionResult instead of result.
• Empty sections created only because the API has that property.
• Long opaque payloads that require the model to reverse-engineer meaning.
• Broad assistant instructions such as IMPORTANT, MUST, CRITICAL, or output that tries to override behavior beyond the current result.

Tool descriptions and parameter .describe() strings remain the right place for durable tool-selection guidance. Result text can include light scoped guidance, but it should not act like a system prompt. See "Response Formatting" in common-patterns.md for examples of acceptable response notes.

Formatting Upstream Data

Translate upstream API shapes into user-facing terms:

• Humanize machine names: event_frequency_count -> Event frequency count.
• Humanize keys: conditionResult -> result, targetIdentifier -> target.
• Flatten nested config only when it improves readability.
• Preserve values exactly when they are user-entered text, slugs, queries, or identifiers needed for follow-up.
• Drop empty, nullish, or unknown placeholder values before rendering details.
• Cap long repeated lists and say how many additional items were omitted.
• Prefer shared helpers for dates, actors, IDs, and unknown values. If a helper emits noisy placeholders for a domain-specific field, filter before calling it.

When changing Sentry API endpoint usage, validate the upstream behavior in ~/src/sentry as required by ../../AGENTS.md. API schemas should model what Sentry returns, but tool responses should model what users need.

Structured Content

MCP tools may expose structuredContent alongside generated text content. Use it when clients need a typed result, pagination token, stable follow-up handle, or machine-readable projection of the same result. The current MCP spec defines structuredContent as a JSON object on CallToolResult, and outputSchema as the schema for that object:

• Choose one response contract per tool: handwritten markdown or structuredContent. Do not hand-write markdown and also return a large structured projection from the handler.
• Exception: markdown tools may include a small structuredContent object for documented continuation hints, such as suggestedActions, when the markdown remains the canonical human-readable result.
• If a tool declares outputSchema, every successful structuredContent result must conform to that schema.
• Return structured results with structuredResult(payload). The server generates content as a compatibility fallback from the same payload.
• When a markdown tool also returns hint-only structuredContent, return a full CallToolResult with both handwritten content and the hint object. Do not use structuredResult(payload) for that mixed response.
• Do not duplicate a large structured payload into a markdown artifact block.
• Treat structuredContent as a stable product contract, not a raw upstream API passthrough. Map only documented fields that callers should depend on.
• Do not spread .passthrough() API schema objects directly into structuredContent; backend-only fields can leak into the public MCP interface.
• Keep names, nullability, arrays, cursors, and URLs aligned between outputSchema, tests, and generated definitions.
• Snapshot structuredContent for structured tools, similar to handwritten content snapshots for markdown tools. Include a regression assertion for fields that must not leak when the upstream response schema is passthrough.
• Test generated compatibility text at the server boundary, not inside structured tool handler tests.
• Use tool execution errors with isError: true for recoverable tool failures. Do not return partial success-shaped structuredContent for errors unless the error shape is explicitly modeled.

Reference: MCP 2025-11-25 Tools specification, sections "Structured Content" and "Output Schema".

Suggested Actions

Use suggestedActions when a tool result reveals a concrete follow-up tool call that a client or agent could offer as a continuation. This is the machine-readable counterpart to a narrow ## Response Notes hint.

interface SuggestedToolAction {
  type: "tool_call";
  toolName: string;
  arguments: Record<string, unknown>;
  reason: string;
}

interface SuggestedActionsContent {
  suggestedActions: SuggestedToolAction[];
}

Guidelines:

• Include only actions that are directly supported by the current result. Do not include broad investigation plans or generic next steps.
• Arguments must be complete enough to call the tool without reparsing markdown.
• Use public MCP parameter names and values, not upstream API field names.
• Respect tool availability in the current session. Omit actions for unavailable tools.
• Keep the list small and ordered by likely usefulness. Prefer one action; use a hard cap of three.
• Keep reason concise and descriptive. It should explain why the action is useful, not instruct the model how to behave.
• Mirror the action in ## Response Notes for clients that do not read structuredContent.
• Do not include secrets, auth tokens, raw payloads, or sensitive user data in action arguments or reasons.

Response Notes

Use response notes for narrow, operational guidance:

• Good: Use get_alert_rule with kind and the numeric rule ID for full details.
• Good: More results are available. Pass cursor: "..." with the same scope.
• Good: Use these details to inspect alert conditions, filters, routing, and notification actions before changing the rule in Sentry.

Avoid implementation jargon:

• Avoid: Treat the returned payload as the canonical source for mutation workflows.
• Avoid: Inspect detector IDs before constructing workflow payloads.
• Avoid: Display these results exactly as written.

Snapshot Policy

Every MCP tool test suite must include at least one representative successful call that snapshots the full formatted handler response. This requirement is defined in ../testing/overview.md and applies to both new tools and meaningful output changes.

When reviewing snapshots:

• Review them as user-facing product output, not only as changed strings.
• Confirm the output includes the fields needed for common real-world questions.
• Confirm internal IDs, raw JSON, and placeholder values are absent unless they are intentionally part of the contract.
• Add targeted negative assertions for known regression risks, such as raw workflow JSON or stale internal fields.
• Include representative upstream internals in fixtures when migrations need to prove that formatting cleans them up.

Partial toContain() assertions are useful for branch-specific behavior, but they do not replace a full-response snapshot.

QA Policy

For output-format changes:

• Run the normal quality gate from quality-checks.md.
• Use the stdio MCP QA path in .agents/skills/mcp-qa/SKILL.md.
• Inspect the raw MCP tool result when possible, not only the LLM's final answer. The test client's final answer can add model-specific phrasing that is not part of the tool response.
• Use a realistic prod prompt that asks for the fields the changed tool should support.

If the raw tool result is clean but the agent final answer adds unrelated content, treat that as a client/agent prompt issue rather than a tool response formatting issue.