Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint=true annotation, the description explicitly discloses 'No DB write, no queue entry, no billing, and the payload is never sent anywhere.' It also clearly states the safety of the operation. The description aligns with and reinforces the annotations without contradiction.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single compact paragraph that front-loads the core purpose, then systematically covers the optional behaviors and ends with safety guarantees. Every sentence adds unique information; no filler or repetition. For a tool with 5 params and heavy nesting, this is exceptionally tight.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description is complete despite no output schema. It explains the return shape, the two modes, and how the optional samples affect results. The complex endpoint schema is fully documented in the input schema, so the description only needs to cover behavioral glue, which it does thoroughly. Nothing an agent needs to call this correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with each parameter described. The description adds value beyond the schema by explaining the conceptual roles: sample drives outgoingMappingEvaluation, answerSample drives answerMappingEvaluation, and that they cannot be inferred from each other ('the two travel in opposite directions'). It also explains the create-vs-PATCH semantic of endpointId. Only minor gap: no examples of actual values, but the schema covers field detail.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear verb ('Validate'), a specific resource ('an endpoint document'), and explicitly contrasts with writing. It immediately distinguishes create vs PATCH via endpointId and shows the dual return shape ({ok:true,...} or {ok:false,...}). This fully disambiguates it from siblings like create_endpoint or update_endpoint.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides explicit when-to-use guidance: 'Pass endpointId to dry-run a PATCH against an existing endpoint; omit it to dry-run a create.' Also explains when to supply sample and/or answerSample and what each does. Though no alternative tool is named, the instructions fully cover the decision points for this tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.