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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds real behavioral context: gap-blocking, future-date resolution order, and the null return when nothing has arrived. The only missing context is whether failures due to gaps surface as errors or as null.

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?

Short, front-loaded sentences with no filler, and the default behavior (omit asOf) appears early. Minor redundancy between the description and the asOf schema text keeps it from 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?

With an output schema present and full parameter coverage, the description only needs the edge-case semantics, which it supplies (gap blocking, future dates, null result). Sufficient to call correctly, though the failure mode for blocked gaps remains unstated.

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%, so both parameters are documented in-schema, including the self-person default for personId. The description's notes on asOf largely restate the schema's own wording rather than adding new meaning, so 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 computation (country inferred from the latest journey arrival) with a time scope, which is clearly distinct from list/get siblings. It does not explicitly name the close alternatives (get_residency_status, check_schengen_status), so an agent must infer the boundary itself.

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 rules: omit asOf for today, how future dates are resolved, and that open journey gaps block the result. It even routes unfamiliar agents to get_tripledger_guide. It stops short of saying when to prefer get_residency_status or check_schengen_status instead.

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