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

Goes well beyond the readOnly annotations: explains how future asOf values are projected (logged journeys first, then assumed continued presence), that open journey gaps block the calculation, and that transit and uncertain days are included. These are exactly the non-obvious behaviors an agent needs before trusting the numbers.

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 core metric and window scope, then edge-case behavior, then the guide pointer — sensible ordering with little waste. The future-date clause is duplicated almost verbatim from the asOf schema description, which is the only real redundancy.

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?

An output schema exists, so return shape needn't be explained; what remains — window definitions, default date, gap-blocking, transit inclusion, and the guide prerequisite — is fully covered. Nothing needed to invoke it correctly is missing.

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 coverage is 100% and the asOf description already carries the future-date and gap-blocking semantics, so the description largely restates the schema. The personId default (self person) is covered in the schema but not in the description; 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?

States a specific resource and metric (days spent per country) with two explicit window types (rolling-365, calendar-year) — clearly not the same output as check_schengen_status or get_residency_status. It stops short of naming those siblings, so differentiation relies on the reader already knowing what they return.

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 usage instructions for the optional parameter ("Omit asOf for today") and an explicit prerequisite route to get_tripledger_guide when the semantics are unfamiliar. It does not state when to prefer this over the other status/summary siblings, so selection between those still takes inference.

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