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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral context by naming exactly what data is returned and by specifying the required credential. It does not disclose error handling for invalid keys, but for a read-only status tool this is a minor gap and there is no contradiction with annotations.

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 description is a single sentence with the scope and key prerequisite front-loaded, followed by a compact list of returned fields. There is no filler or redundant content. The list is slightly dense but remains readable and information-dense.

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 one-parameter, read-only tool with rich annotations, the description is mostly adequate. It enumerates the return fields and the required key. However, domain-specific terms such as 'rail', 'terms', and 'states' are left unexplained, and with no output schema the agent may not fully understand the semantics of the returned data.

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 for the single parameter buyer_key is 100%, so the baseline is 3. The description's 'Requires the buyer key issued at confirmation' mostly duplicates the schema's 'Issued to the licensed contact at confirmation'. It adds no real format, validation, or usage detail beyond what the schema already provides.

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 explains that the tool reports status for a registered agency and enumerates the returned attributes: states, rail, terms, founding period, queued/delivered counts, credit balance, and licence verification. It lacks an explicit action verb such as 'retrieves' or 'gets', but the title and 'For a registered agency' make the purpose clear. It also differentiates from siblings by requiring the buyer key issued at confirmation.

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 states a clear prerequisite: the agency must already be registered and the caller must have the buyer key issued at confirmation. However, it gives no explicit guidance on when to choose this tool over siblings like check_eligibility, register_agency, or pull_requests, and no when-not-to-use exclusions. Usage context is implied rather than explicitly routed.

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