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

Annotations already declare readOnlyHint and non-destructive, so the description focuses on behavior the annotations can't express: the rolling-window semantics, extrapolation for future dates, and the hard failure mode where open journey gaps block the calculation. That failure mode is genuinely useful pre-call context. It doesn't describe output shape, but an output schema exists.

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?

Front-loaded with the resource and its outputs, then constraints, with the guide prerequisite last. Sentences are dense but each carries information; nothing is padding. Slightly compressed syntax ("90-in-180-day") costs a little readability.

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 read-only calculation tool with an output schema and fully described parameters, the description covers the non-obvious parts: window interpretation, future-date extrapolation, and the gap blocker. What's missing is a pointer to the sibling that answers the closest adjacent question (residency status).

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 already documented in the schema, and the description's asOf text largely restates the schema's own wording. personId is never mentioned in the description. Baseline 3 is appropriate when the schema does the heavy lifting.

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 domain (Schengen 90-in-180-day compliance over a rolling window) and enumerates the outputs: days used/remaining, per-country breakdown, per-trip detail. An agent can tell this is a calculation/report tool rather than a mutation. It does not explicitly contrast with the nearby get_residency_status, which is the main source of residual ambiguity.

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?

Gives concrete invocation rules: omit asOf for today, future dates honor logged journeys then continue presence in the last destination, and open journey gaps block the calculation. It also routes an unfamiliar agent to get_tripledger_guide first. It stops short of saying when to prefer this over get_residency_status or detect_journey_gaps.

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