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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the bar is lower, yet the description still adds substantial context: live retrieval from the GOV.UK Content API, a 1-credit cost, the output shape (headed plain-text subsections), and an explicit caveat that the destination's own authorities set and enforce the rules. The passport-nationality scope limitation is a real behavioral disclosure an agent could not infer from structured fields.

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 capability question, then immediately the returned section, then source, audience caveat and cost — a sensible information order with no filler sentences. It is dense with clauses, but each clause (output format, source, nationality scope, credit cost) carries distinct value rather than repeating structured fields.

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 one parameter and no output schema, the description must carry the return-value burden — and it does by naming the subsections and format returned. It also covers data provenance (live GOV.UK API), audience limits and cost, leaving nothing an agent needs to decide whether and how to call it.

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 sole 'country' parameter's description already documents accepted forms (country name, alternative name such as city or island, GOV.UK slug, e.g. "spain"). The tool description only restates 'for one country' and adds no further syntax or disambiguation guidance, 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?

Opens with the concrete user question it answers and then states precisely what it returns: the FCDO 'Entry requirements' section for one country, enumerating the subsections (passport validity, visas and length of stay, dual nationals, vaccine certificates, customs rules). That enumeration distinguishes it from siblings such as travel_advice_health, travel_advice_safety and travel_advice_warnings_insurance without having to name them.

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?

Usage context is explicit — visa and passport-validity questions for a single country — and it adds a meaningful applicability constraint: written for travellers on a full British citizen passport, with other nationalities directed to the destination's embassy. It stops short of naming sibling tools (e.g. travel_advice_health for vaccination/jab advice) or stating when-not-to-use cases, so it falls short of a 5.

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