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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully adds the shape of the returned record (name, email, phone, username, parent customers), which matters because there is no output schema, but it says nothing about error behavior for a missing id or rate limits.

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?

One tight sentence that front-loads the action and scope, then lists returned fields. The trailing 'GET /user/{user_id}' endpoint is marginally useful for debugging but borders on filler.

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 with annotations covering safety, this is largely complete, and enumerating return fields substitutes for the absent output schema. Minor gaps remain around not-found behavior, which an agent might reasonably want to know.

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% and the single parameter is fully documented in the schema. The description's 'by user_id' restates the schema's 'The user_id (a number)' without adding format, range, or lookup-failure semantics, so the 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?

The description gives a specific verb ('Get one contact') and resource, and the qualifier 'one' separates it from the sibling chargeover_list_contacts. It also clarifies that a 'contact' is a 'user', which resolves naming ambiguity. It falls short of 5 only because the sibling it contrasts with is not named explicitly.

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?

There is no statement of when to use this tool versus chargeover_list_contacts or chargeover_get_customer, nor any prerequisites. The single-record scope implies lookup-by-id usage, but nothing is spelled out.

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