aps_capability_issue_challenge

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

With no annotations provided, the description carries the burden of behavioral disclosure. It does reveal that the tool signs an action statement, returns a challenge and hash, and is part of binding gateway policy evaluation. However, it does not state whether the operation is non-mutating, idempotent, or whether specific permissions or key formats are required beyond the schema.

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: three sentences plus a search keywords line. It front-loads version and protocol context, clearly states the action and return values, and ends with useful search tags. Every sentence earns its place with no filler.

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?

The tool has 7 parameters with nested objects and no output schema, so the description must compensate. It provides the purpose, return fields, and usage context, but does not explain the structure of the challenge, error conditions, or how to handle the signing keys. The info is sufficient for a basic understanding but not fully complete 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?

Schema description coverage is moderate (71%), not high enough to avoid additional parameter guidance. The description only references the 'action' parameter via 'signed canonical action statement' and does not explain optional parameters like validity_seconds or required_policy_freshness, leaving a gap for these self-explanatory but undocumented fields.

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 action: 'Sink issues a signed canonical action statement' and returns the SinkChallenge and its challenge_hash. This clearly identifies both the function and outcome, and the tool name 'issue_challenge' plus context 'capability-token sink challenge (M1)' distinguishes it from sibling tools like aps_capability_evaluate_authority or aps_capability_sign_effect.

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 provides clear contextual usage: it is used in capability-token flow step M1 to 'bind the gateway's later policy evaluation to a specific action the sink authored.' This implies when to use the tool (as a precursor to gateway evaluation) but does not explicitly mention when not to use it or name alternatives, which is a minor gap.

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