ack_sign_credential

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

With no annotations, the description carries the behavioral burden, and it does state the output behavior ('returning a signed JWT string') and the verification follow-up. It does not disclose behavior on key/DID mismatch or algorithm details, but for a pure signing action the core behavior and result are transparent enough.

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?

Three tightly focused sentences with no filler. The core purpose is front-loaded, and the input-source and verification guidance each add necessary workflow context.

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 three-required-parameter tool with full schema coverage and no output schema, the description closes the loop: where inputs come from, what is returned, and how to use the result. Nothing essential is missing for selecting and invoking the tool.

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 100%, so the baseline is 3 even without extra parameter descriptions in the tool description. The prose mostly restates the schema hints about where credential and signerJwk come from, adding little additional meaning beyond what the schema already provides.

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 ('Sign'), a precise resource ('a W3C Verifiable Credential'), and the return type ('a signed JWT string'). It also anchors the tool in a workflow by naming related creators and verifiers, which distinguishes it from generic JWT tools like ack_create_jwt.

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 gives explicit usage context: pass output from ack_create_controller_credential or ack_create_payment_receipt as credential, and verify the result with ack_verify_credential or ack_verify_payment_receipt. It does not explicitly say when not to use it versus ack_create_jwt, but the W3C VC framing makes the intended context clear.

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