zipviz_sign_message

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

With no annotations, the description carries the full burden and does well: it discloses that signing is local with the configured agent key, that there are no network calls, the canonical payload shape, and the exact return fields (base64 signature, timestamp, signing_version:1). It also explains the key_path rejection and the security reason behind it. Missing only failure behavior (unconfigured key/domain) and any permission prerequisites.

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?

Front-loaded with the action and key mechanism, followed by two short sentences covering the contract and the return shape. Every clause carries information; no filler or repetition of the tool name.

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?

With no output schema and no annotations, the description compensates fully: it documents the return values, the signing format, the local-only behavior, and the rejected parameter. An agent has everything needed to invoke this correctly and chain it into zipviz_send.

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 100%, so baseline is 3, but the description adds genuine meaning beyond the schema by mapping the parameters onto the canonical envelope {v:1, from, message, timestamp} and explaining why the timestamp must be read back from the return value rather than re-supplied. That ties the parameters together semantically rather than restating them.

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?

Specific verb+resource ('Sign a message locally with an agent's configured Ed25519 private key') plus the exact envelope contract that api.zipviz.ai /v1/verify accepts. This clearly distinguishes it from siblings like zipviz_verify and zipviz_send without needing to open their schemas.

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?

States the operational context ('No network calls') and routes the follow-up case explicitly: callers that must send the timestamp alongside the signature, e.g. zipviz_send, should read it back from the return value. It stops short of naming a when-not condition or pointing to zipviz_verify as the counterpart, so it is clear context rather than full routing.

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