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

Annotations already declare readOnly, idempotent, non-destructive and closed-world. The description adds genuine value beyond them by disclosing the shape of the returned data (expenses with payer and split, travelers with ID, name, and which is the user), which is not in any structured field since there is no output schema.

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 tight sentences with no filler: content/scope first, then the ID-lookup use case, then the summary alternative. Every sentence earns its place and the most actionable routing info is front-loaded.

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 no output schema, the description compensates by summarizing what is returned, and with only two fully-documented params and annotation coverage of the safety profile, nothing an agent needs to select or call this tool 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 description coverage is 100% – both 'query' (description/vendor/category match) and 'trip_id' (Tineo trip ID from trips_list) are fully documented in the schema. The description does not add syntax or format meaning beyond that, so the baseline of 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?

The description names a specific verb+resource ('List a trip's individual expenses') and adds scope detail (who paid, how each is split, plus travelers with ID/name/user flag). It is unmistakably distinct from get_trip_expense_summary and the expense write tools.

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?

Explicitly states when to use it ('to find an expense or traveler ID before trip_expense_update or trip_expense_create') and names the alternative for the other intent ('For totals and who owes whom use get_trip_expense_summary'). Both the routing condition and the excluded sibling are given.

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