Explain a denied capability

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

With no annotations present, the description carries the full burden of behavioral disclosure. It clearly states the tool's purpose but does not mention side effects, permissions, or that it is a read-only operation. The phrase 'refused' implies it is explanatory, but the description does not explicitly say whether it executes anything or how it behaves beyond returning an explanation. This is adequate but not rich; a 3 reflects the absence of contradictions balanced against incomplete behavioral detail.

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 two sentences with zero redundancy. The primary purpose is front-loaded, and the usage guidance follows immediately. Every word earns its place without padding.

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 simple tool with one enum-constrained parameter and no output schema, the description provides sufficient context: it explains what it does and when to prefer it over requesting capabilities. It does not describe the return format or potential errors, but given the simplicity and the absence of an output schema, this is a minor gap. Completeness is high for the tool's complexity.

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 provides 100% coverage: the single parameter 'capability' has an enum list and a description that fully defines it as 'A capability from the published deny-list.' The description adds no extra semantics beyond referring to a 'named capability,' which is already covered by the schema. Given high schema coverage, the 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 a clear verb-resource purpose: 'Explain why a named capability is refused.' It also distinguishes itself from asking the server to grow a shell, HTTP client, or secret reader, which positions it as a diagnostic tool rather than a capability-granting one. However, it does not explicitly name the sibling tools (list_catalog, lookup_api, etc.) or contrast with them, so some differentiation is left implicit.

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?

It provides explicit guidance on when to use this tool: 'Use this instead of asking the server to grow a shell, HTTP client, or secret reader.' This tells the agent that whenever it would consider requesting such capabilities, it should instead call explain_deny. It does not mention the sibling tools or give extensive exclusion criteria, but the core use case is clearly stated.

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