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

Annotations already declare readOnlyHint=true, covering the safety profile, so the bar is lower. The description usefully adds the underlying Accelo API mapping (GET /api/v0/contacts/{id}) and the response envelope shape { meta, response }, but says nothing about error behavior or missing/invalid ids.

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?

Two short sentences, front-loaded with purpose followed by implementation detail; no filler. Slightly terse, but nothing is wasted.

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?

For a simple read-only single-resource fetch, the description plus annotations plus 100% schema coverage cover what an agent needs; the response envelope is even disclosed despite there being no output schema. Missing only error-case hints.

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 description coverage is 100%, so both parameters (id, fields) are already documented in the schema, including the _fields syntax and "_ALL". The description adds no parameter meaning beyond the schema, so baseline 3 applies.

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?

States a specific verb and resource ("Fetch a single contact (a person)") and the word "single" implicitly separates it from the list_contacts sibling. It stops short of naming alternatives explicitly, but an agent can identify the operation without opening the schema.

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?

Usage is only implied by "single contact" and the required id parameter; there is no explicit when-to-use, no exclusion criteria, and no pointer to list_contacts/search alternatives. Adequate but leaves the agent to infer routing.

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