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

The readOnlyHint annotation already covers safety, so credit goes to what the description adds: the identity/scope of the lookup (token-derived), the returned field set, and the cost signal ('cheap'). With no output schema, disclosing the return contents is genuinely useful information the agent cannot get elsewhere.

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 plus an API endpoint citation, with the purpose front-loaded before the when-to-use rationale. Nothing is padded and every clause carries information.

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 zero-parameter tool with no output schema, the description supplies the returned field list and the reason to call it, which covers the practical gaps. The only shortfall is the absence of any error/auth-failure behavior guidance, which is minor given the simplicity.

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 tool takes zero parameters, so the baseline is 4. The description correctly implies no input is needed since the token is the implicit subject, and nothing is left ambiguous about what to supply.

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 ('Return the Deputy user the token belongs to') and enumerates what comes back (name, employee id, company, permissions). This clearly separates it from siblings like deputy_get_employee, which take an employee identifier rather than resolving the token owner.

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?

'A cheap way to confirm DEPUTY_INSTALL and the token are right' gives an explicit use context, so the agent knows when this diagnostic identity check is warranted. It does not name an alternative or state exclusions, which keeps it short of a 5.

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