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

The description adds the useful side-effect note 'It writes nothing in the expense-tracker server; only mark_exported changes this trip', but this directly contradicts the readOnlyHint annotation because mark_exported can stamp exported_at on the trip. Since the description contradicts the annotations, the rubric requires a score of 1.

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?

The first two sentences are tight and front-loaded with purpose and side-effect behavior. However, the trailing 'Pro.' is an unexplained fragment that adds no information and makes the description feel unfinished.

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 communicates the core return shape (one or two payloads) and the main safety constraint. It does not enumerate the exact expense_add payload fields, but those are presumably defined by the referenced expense_add operation, and the schema already covers all parameters.

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?

All five parameters already have schema descriptions, so the baseline is 3, but the description adds meaningful context: split_lodging changes the payload count, and mark_exported is the only path to mutation. It does not repeat the schema's field-by-field details, which is appropriate.

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 verb is precise: 'Return the exact expense_add arguments for a saved trip', and it describes the output shape with one subsistence payload and an optional lodging payload. This clearly distinguishes it from trip_record, trip_list, and trip_delete in the sibling set.

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?

The description frames the tool as being for saved trips that need expense_add payloads, and it flags the mark_exported side effect, giving an agent enough context to decide when to call it. It does not explicitly name alternatives or when-not-to-use conditions, but the intended use case is clear.

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