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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely non-obvious context: the exact field set returned and the critical caveat that amounts are bare numbers with no currency attached. It does not discuss error behavior for a bad UUID, but that is minor.

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, front-loaded with what the tool returns, then sibling differentiation, then the currency caveat. No filler or restatement of the title.

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 takes on the burden of describing return contents and does so by enumerating fields and related entities. Combined with the currency warning and the sibling distinction, an agent has everything needed to call and correctly interpret this tool.

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% for the single 'id' parameter, so the schema already documents it fully. The description's 'by ID' adds nothing beyond the schema; baseline 3 applies when structured data does the work.

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 ('Get a single asset cost record by ID') and anchors it to a concrete UI surface (the AssetLab 'Expenses' page). It also lists the returned fields, so an agent knows exactly what this record contains versus other cost-like records.

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 names the sibling it is confused with ('Distinct from get_expense (project-scoped expenses without invoice/PO)') and states the distinguishing condition. It also gives a prerequisite action for interpreting the result (call get_organization_settings for currency_code before stating a currency).

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