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

readOnlyHint=true already declares the safety profile, so the description's added value is disclosing the return payload ('with teams and departments'), which is useful given there is no output schema. It does not cover auth needs, error behavior, or whether both lookup keys can be combined.

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?

Very compact and front-loaded, leading with the resource and lookup keys. The trailing 'GET /users/{identifier}' is largely redundant restatement of the endpoint, keeping it just short of a 5.

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 single-read tool with full schema coverage, a readOnly annotation, and no output schema, the description is nearly sufficient, even naming the nested data returned. Minor gap: no statement of what happens on a missing/ambiguous identifier or whether one of the two optional params is required.

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 are fully documented in the schema, establishing the baseline of 3. The description's 'user id or email address' merely echoes the schema and does not clarify the mutual-exclusivity/precedence between the two optional keys.

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 ('One employee') plus the lookup keys (user id or email) and the extra data returned (teams and departments). This clearly contrasts with the plural list_users sibling via 'One employee', though it never names that sibling 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?

The singular-resource framing implies you use it when you know an id or email, but there is no explicit when-to-use or when-not guidance and no mention of list_users as the alternative for discovery. Usage is inferable rather than stated.

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