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

Annotations provide readOnlyHint=true, so the read-only nature is already disclosed. The description adds the REST endpoint (GET /contacts/{id}) which reinforces idempotence but does not disclose additional behavioral traits like error handling, pagination, or rate limits. It meets the baseline but adds minimal context beyond annotations.

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 two short sentences that immediately state the purpose and the REST endpoint. No redundant information, front-loaded with the action, and every word earns its place.

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?

This is a simple single-parameter read-only getter. The description sufficiently covers what the tool does and which parameter it requires. No output schema exists, but the return value (a contact) is implied and no complex behavior needs explanation. The context is complete for this level of complexity.

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?

The input schema fully describes the only parameter 'id' as 'The contact id.' with a 100% coverage rate. The description's mention of 'by id' and the REST path /contacts/{id} reiterate the same meaning without adding new constraints or formatting details. Baseline of 3 is appropriate given high schema coverage.

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 clearly states 'Get a single contact by id', which uses a specific verb and resource. It distinguishes from siblings like list_contacts and search_contacts by focusing on a single record lookup via id. The REST endpoint adds precision.

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?

The phrase 'single contact by id' clearly implies this tool is for fetching one specific contact when the id is known. It does not explicitly mention alternatives (e.g., list/search) but the context is unambiguous. No explicit exclusions are provided, but the usage context is well defined.

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