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

Beyond the destructiveHint annotation, the description reveals how the sensitive value is handled (secret store, only last four retained), that the response returns nothing, and that the full number is never readable back. This is exactly the irreversibility and privacy context an agent needs.

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?

Five sentences each carry distinct information: purpose, format, storage, return behavior, and an anti-hallucination guardrail. There is no filler or redundant restating of schema fields.

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 two-parameter mutating tool, the description covers format, privacy, irreversibility, and the missing-EIN edge case, while the output schema handles return expectations. The only notable omission is the behavior when ein is omitted, since the schema marks it optional.

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?

The description enriches 'ein' beyond the schema pattern by specifying no separators and the storage/truncation behavior. The 'applicationId' parameter is left mostly to the schema's 'UUID value wrapper' description, but the tool description's reference to 'a banking application' provides enough context.

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 opening sentence names a specific verb ('files'), object ('company's EIN'), and target ('banking application'), and adds the exact format constraint. This is enough to distinguish it from similar siblings like banking_set_owner_tax_identifier.

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 gives a clear contextual trigger and an explicit when-not-to-call rule: if the EIN has been applied for but not received, report that instead of inventing digits. It does not name a sibling alternative, but for this narrow set-style tool the context is sufficient.

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