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

Annotations already declare readOnly=false, idempotent=true and destructiveHint=false; the description earns credit for adding the auth prerequisite, the batching limit, and the duplicate-skip rule that explains the idempotency hint. It also discloses refund estimation semantics, which is real behavioural context an agent would otherwise lack.

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 action and limit, then flags, dedupe and refund rules in a tight sequence. Dense but each sentence carries information; the refund-rule sentence is the only one that could be trimmed given the schema already covers it.

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 still covers safety-relevant behaviour via annotations, auth requirement, batch cap and duplicate handling. Minor gaps remain around what happens on partial failures or how rows beyond 500 should be submitted, but nothing critical is missing for correct invocation.

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 every field, including the flag booleans and the deprecated is_max_fare, is documented inline. The description's discussion of flags and intended_destination largely restates what the schema already says, so it adds only marginal meaning beyond the structured fields; 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 verb and resource ('Adds TfL contactless journeys to the person's Untap account') plus the per-call limit and the post-save checking behaviour. It never names check_tfl_journeys explicitly – only alludes to 'the TfL check' – so an agent must infer how this differs from that sibling, which keeps it below a 5.

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 useful operating context: sign-in requirement, 500-row ceiling and that already-saved journeys are skipped, which implies safe re-running. It does not say when to prefer this over check_tfl_journeys or what to do with statements larger than 500 rows, so usage is implied rather than prescribed.

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