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

Annotations already declare a safe read operation, and the description adds real value on top: deleted or merged contacts return 404, and another user's contact also returns 404, which tells the agent that access is owner-scoped and that not-found masks permission. It stops short of saying whether the 404 is distinguishable or what the returned object contains.

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 what is returned, followed by the identifier contract and the failure modes. No redundant restatement of the title or annotations.

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 one-parameter read tool this covers the identifier formats and the failure semantics, which is most of what an agent needs. With no output schema, the description could have sketched the returned contact's shape, but the gap is minor for a standard lookup.

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 0%, so the description carries the burden for the single parameter, and it does: `id` accepts either the internal id or the publicId formatted like `CS-0042`. That is meaningful format guidance absent from the schema, though it does not clarify whether the two forms are interchangeable in all cases.

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?

"Returns one contact" gives a specific verb and resource with an explicit singular scope, which implicitly separates it from the list-style sibling contact_find. It never names contact_find or contact_change, so differentiation is left to inference rather than stated.

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 description makes clear this is the single-record lookup keyed by an identifier, but it never says when to prefer it over contact_find (search by other criteria) or contact_change (mutate). Usage is implied by the required `id` rather than stated as guidance.

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