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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real value beyond that: it discloses the result cardinality ('up to 5 matches'), what the matches contain (ids), and a hard-coded exception that would otherwise cause a silent wrong call. It stops short of noting what happens on zero matches or whether the query is normalized, which keeps it from a 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?

Three short sentences, each doing distinct work: purpose, return contract plus downstream use, then the exclusion. The most failure-prone information (the Gatwick carve-out) is placed last where it is still prominent, and no sentence restates the title or annotations.

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 one-parameter lookup with no output schema, the description covers what goes in, what comes back in shape and quantity, how the output is consumed downstream, and the single known edge case. Annotations handle the safety semantics, so nothing an agent needs to call this 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 single parameter already carries an example, so the baseline is 3. The description still adds meaning by naming the accepted categories of input (street address, postcode, station, hotel), which is broader than the schema's two examples and tells the agent free-text user utterances are acceptable.

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 verb and resource ('Look up a UK pickup or drop-off place') and enumerates the entity types it resolves (street address, postcode, station, hotel). It also names the downstream consumer (get_quote) and the one case it must not be used for, so an agent can separate it from siblings without opening a schema.

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 an explicit use case (resolving a place to ids that feed get_quote) and an explicit exclusion with the alternative to use instead ('Not for Gatwick Airport: use the ids gatwick_north or gatwick_south'). When-to-use, when-not-to-use, and the substitute are all present.

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