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

Annotations declare destructiveHint=true, and the description adds important behavioral context: the document number goes to a secret store, only country and expiry are recorded on the owner, and the response returns nothing. This goes beyond the annotation by explaining what is stored, what is not stored, and the return behavior. It doesn't fully explain the destructive implications, but the annotation already signals that.

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 sentences with no filler. The core action and scope are front-loaded, followed by storage/return behavior, then the sibling routing and usage instruction. Every sentence earns its place.

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 3-parameter tool with an output schema and annotations, the description covers the action, the alternative tool, the storage behavior, and the return value. It doesn't mention the exact format of the passport number (though the schema pattern covers that) or what happens on duplicate submission, but the description is complete enough for an agent to invoke it correctly.

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 67% (applicationId and ownerId are described as UUID wrappers, but documentNumber has no schema description). The description compensates by explaining the documentNumber's role, its destination (secret store), and the fact that only country and expiry are recorded. It adds meaning beyond the schema for the key parameter.

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 states a specific verb ('Files'), a specific resource ('a non-US beneficial owner's passport number against a banking application'), and the exact scope (non-US owner without SSN/ITIN). It also explicitly distinguishes itself from the sibling 'tax-identifier' tool, so an agent can tell them apart without opening schemas.

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 explicitly says when to use this tool ('Use this instead of the tax-identifier tool for an owner who has no SSN or ITIN') and gives a clear exclusion condition. It also instructs to pass the document number once and not repeat it back, which is actionable usage guidance.

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