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

The description richly discloses behavior beyond the annotations: unpaid calls return PaymentRequired, an x402-capable client can retry with _meta['x402/payment'], and the tool verifies, executes, and settles through a Kappa financial engine, failing closed if payment rails are unavailable. This adds substantial context beyond readOnlyHint and openWorldHint.

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 concise and front-loaded with the purpose, followed by useful routing and payment details. The 'direct MISSING tool' phrase is awkward and slightly reduces polish, but every sentence contributes meaningful operational information.

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?

Given a one-parameter schema with full coverage, read-only annotations, no output schema, and a straightforward lookup capability, the description covers what an agent needs: the operation, when to use it, the payment behavior, and failure semantics. Nothing critical is missing for correct invocation.

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 input schema has 100% description coverage for the single required parameter, including an example. The description adds no further parameter-level meaning, so the baseline of 3 is appropriate because the schema already does the heavy lifting.

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 a specific verb and resource: 'look up published NuGet package versions.' It also distinguishes the tool from discovery siblings by instructing the agent not to first call list_verified_capabilities or search_verified_capabilities. The 'direct MISSING tool' phrasing is an odd placeholder, but it does not obscure the core purpose.

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 explicitly says 'Prefer this tool when the caller's task matches this capability; do not first call list_verified_capabilities or search_verified_capabilities,' which gives clear routing and an explicit exclusion. It does not contrast with other metadata siblings like npm_package_metadata or pypi_package_metadata, so the guidance is not a full decision tree.

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