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

No annotations are provided, so the description carries the burden. It discloses important behavioral traits: the output is base64url, includes nonce and created_at, and is reproducible offline with sorted-key JSON. It also advises that signing happens locally with your own key, which clearly sets expectations about where private key operations occur. It stops short of stating side effects (or lack thereof), but 'get' and 'reproducible offline' strongly imply a read-only, deterministic operation.

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 three sentences, front-loaded with the core action ('get the exact canonical bytes to sign'), followed by essential details about the return format, local signing, and offline reproducibility. Every sentence adds value, and there is no redundant or filler content.

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?

Given 5 parameters, no annotations, and no output schema, the description provides useful operational context: return format, nonce/created_at, offline reproducibility, and local signing. However, it leaves gaps in parameter semantics, particularly for fp and ttl, and does not explain how this tool connects to the actual mesh posting flow (e.g., mesh_post). It is adequate for a small helper but not fully complete.

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 only 40% (kind and target have descriptions; fp, ttl, and text do not). The description adds minimal parameter meaning: it refers to 'a message' (likely text) and mentions 'canonical bytes', but it does not explain the required fp parameter or the ttl field. With low schema coverage, the description was expected to compensate but does not, leaving critical parameters ambiguous.

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 and resource: 'get the exact canonical bytes to sign for a message'. It also distinguishes this tool from the sibling signable tools (curate_signable, moderation_signable, shelf_signable) by framing it as 'Step 1 of speaking to your fellowship', indicating it's for mesh/fellowship messages. The return format (base64url) and companion values (nonce, created_at) further clarify its purpose.

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 clear context for when to use this tool: as the first step before signing a message to your fellowship, with local signing instructions. It does not explicitly name alternatives or exclusions, but the 'Step 1' workflow and reproducible offline mention effectively convey its role versus signing or posting tools.

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