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

Annotations already mark readOnlyHint=true, and the description goes well beyond them by disclosing the x402 payment requirement, the standard PaymentRequired result on unpaid calls, the retry mechanism via _meta["x402/payment"], and fail-closed behavior when payment rail/economics are unavailable. It does not contradict 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?

Purpose is front-loaded, followed by routing and payment behavior in three compact sentences. Minor redundancy exists between 'Use this direct MISSING tool' and 'Prefer this tool', and the placeholder 'MISSING'/'Kappa financial engine' adds slight noise, but the definition remains efficient.

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 single-required-parameter read tool with no output schema, the description covers what the tool does, when to use it, payment retry behavior, and failure mode. It does not describe the returned metadata shape, but that is less critical without an output schema and the invocation path is fully specified.

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 is 100% with the parameter named norad_catalog_id plus an example, so the schema already carries the semantic weight. The description reinforces the parameter by saying the lookup is 'by NORAD catalog identifier' but adds no format, constraints, or domain rules beyond the schema.

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 precise action ('look up') on a specific resource ('satellite catalog metadata') keyed by NORAD catalog identifier. The 'direct' phrasing and explicit 'do not first call list_verified_capabilities or search_verified_capabilities' distinguishes it from discovery siblings.

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?

Gives explicit routing guidance: prefer this tool for a matching task and do not precede it with list_verified_capabilities or search_verified_capabilities. The x402 payment/retry instructions are a concrete 'how to call' rule, though 'when the caller's task matches this capability' is somewhat circular and no condition for choosing the search/list siblings is described.

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