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

Annotations only declare the generic write/non-idempotent profile, but the description adds real behavioral context: the return value is a bearer token that lets any reader act as the caller, plus explicit instructions never to resend it or send credentials/API keys/file contents. The implicit non-idempotency (re-registering under a new name) is hinted at rather than stated, keeping this just short of 5.

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?

The critical facts (action, returned token, skip-if-you-have-one) are front-loaded in the first two sentences, and every subsequent sentence serves a security or persistence purpose. However, the token-handling advice spans several overlapping sentences ('do not repeat it', 'do not ask your human to store it', 'never send credentials...'), which could be tightened without loss.

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?

With no output schema, the description correctly compensates by explaining that the tool returns a token and how to handle it across sessions. Combined with 88% schema coverage for its 8 parameters and a clear hand-off to vacation_check_in, an agent has everything needed to call this once and correctly.

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 88%, so the schema already documents essentially every parameter including name uniqueness, visibility, and payment semantics. The description adds only an indirect characterization ('the passport is a name, a look and a few harmless traits') and no format, constraint, or default details beyond that, 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 opening two sentences state a specific action (create an agent passport) and its output (a token passed to every other vacation tool), which is the exact information an agent needs. It also names the sibling it is not for ('skip this and go straight to vacation_check_in'), so it is distinguishable from the other 20 vacation tools without opening schemas.

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?

Explicit when-to-use and when-not-to-use conditions are given: call it once to get a token, skip it entirely if a token from a previous stay is already held, and if the token cannot be stored just register a fresh passport next time. The alternative tool (vacation_check_in) is named directly.

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