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

Annotations already convey readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds that the buyer key is 'issued at confirmation' and that the licence verification status is included, but it doesn't disclose rate limits, response size, or what happens if the key is invalid. Given the annotations, a 3 is appropriate – the description adds some value without contradicting or richly extending the annotation context.

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?

A single, dense sentence that front-loads the purpose ('For a registered agency') and then lists the output fields efficiently. Every word carries information; there is no fluff. It could be slightly improved by separating the parameter requirement into a second sentence, but it remains clear and compact.

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 read-only status lookup with one parameter and no output schema, the description covers the main inputs and outputs. It does not explain error cases (e.g., invalid buyer key, unregistered agency), return format, or pagination, but these are minor given the tool's simplicity and the annotations covering safety. It is adequate but not exhaustive.

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%, so the schema already documents the buyer_key parameter's meaning ('Issued to the licensed contact at confirmation'). The description reinforces this by stating the key is required for a registered agency, but adds no new semantic details about the parameter itself. Baseline 3 is correct.

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 ('requires', 'returns') and resource (agency status), and enumerates the exact fields delivered: states, rail, terms, founding period, queued/delivered counts, credit balance, licence verification. The mention of 'registered agency' and the required buyer key makes its scope clear. It does not explicitly differentiate from siblings like check_eligibility, but the listed fields make its purpose reasonably distinct.

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 implies usage: it is a read-only status lookup for a registered agency using the buyer key. It does not explicitly say when to use it instead of siblings (e.g., check_eligibility) or when not to use it. The prerequisite (being a registered agency with a buyer key) is stated, providing some usage context.

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