aps_capability_sign_effect

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

With no annotations provided, the description carries the full burden and does well: it discloses the nullifier replay rejection, token consumption, action execution, and signing of the EffectReceipt binding token to result. This goes beyond what the schema or name alone would convey, though it does not mention reversibility or permission requirements.

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 dense sentences plus search keywords. It is front-loaded with the version and role, and every sentence adds value—protocol position, behavior, and attestation context. No wasted words.

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?

There is no output schema, so the description should clarify what the tool returns. It says 'signs an EffectReceipt' and mentions the attestation tuple, implying the receipt is the output, but it never explicitly states the return value or error cases beyond nullifier replay. For a complex protocol tool with 7 parameters, this leaves a noticeable gap.

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 57%, with challenge, challenge_receipt, and gateway_public_key already described. The description adds protocol context (M3 preimage, M1 binding) but does not explicitly explain sink_private_key, sink_public_key, or the effect object structure beyond what the schema already shows. It partially compensates but not fully.

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 uses specific verbs and resources: 'consumes the token preimage', 'executes the action', and 'signs an EffectReceipt'. It clearly identifies this as the M4 sink step in the capability-token protocol, distinguishing it from sibling tools like aps_capability_issue_challenge and aps_capability_mint_receipt.

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 protocol sequencing: it must be invoked after the gateway's M3, consuming the token preimage from that step. It references the (M1, M3, M4) tuple, which implies the prerequisite context. However, it does not explicitly state alternatives or when not to use this tool, so it misses the full top score.

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