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

With no annotations, the description carries the burden. It discloses that unpaid requests return HTTP 402 and that a valid X-PAYMENT yields JSON, which is useful. However, it does not mention that it is a read-only GET, any rate limits, or what happens on other errors. The cryptic 'Not a new SKU' adds confusion rather than clarity.

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 run-on sentence with multiple clauses, including payment details, endpoint, response condition, and a confusing note. It is compact but not well-structured; the information could be presented more clearly with separation of payment requirements from tool behavior.

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 paid API endpoint, the description lacks essential details: how to obtain payment, what the JSON contains, whether there are limits, and how this differs from the many sibling mariners tools. The absence of an output schema makes it even more critical to describe the response, which is not done. It is inadequate for an agent to fully understand and use this tool 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?

The single parameter x_payment is fully described in the schema with a clear explanation that it is forwarded as a header. The description reinforces that a valid X-PAYMENT is required for JSON, adding context about its necessity, but it does not add new meaning beyond the schema's description, so a baseline of 3 is appropriate.

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 it is a GET endpoint that returns JSON after payment, and mentions 'USCG D17 / Alaska LNM' which implies a specific data domain, but it does not clearly state the resource or what data is retrieved. It is distinguishable from siblings by the D17 suffix, but the purpose is more about the payment mechanism than the action itself.

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 does not compare this tool to any of the many mariners-* siblings. It implies usage for D17 via the name and 'USCG D17 / Alaska LNM', but it does not explicitly say when to use this versus other mariners tools, nor does it mention prerequisites like having a payment mechanism set up beyond the X-PAYMENT header.

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