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

Annotations already signal a non-readOnly, idempotent, non-destructive mutation, and the description reinforces this with a valuable side-effect statement: 'Previously queued publication snapshots remain unchanged. Never publishes.' This tells the agent the change is scoped to future content and has no publishing side effect, adding real context beyond the annotations. Permission/auth requirements are still undisclosed.

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 dense, front-loaded sentences that lead with the use case and then branch on target/mode; every clause carries information and nothing is redundant. Minor terseness ('inherit follows their defaults') slightly hurts readability but not economy.

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 an output schema present the description needn't explain returns, and it covers the mutation's side-effect boundary and mode semantics well. The only real gap is the undocumented draftId/channelId parameters, which leaves the definition slightly under-specified for a 4-parameter 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 0%, so the description carries the burden. It explains the enums that matter — target values (default/channel/post) and selection.mode (inherit/none/custom) plus signatureId — but leaves draftId and channelId entirely undocumented, so half the parameters remain opaque in both schema and description.

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?

States a specific action (assign a signature) and its three scopes (account default, channel override, single-post override), so an agent knows exactly what the tool mutates. It clearly reads as a configuration-assignment tool rather than a create/update-signature tool, though it never names the sibling tools (create_signature, update_signature) it must be distinguished from.

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?

'Use this when managing post auto-signatures' plus the per-target rule ('For default use custom/none; for channel/post inherit follows their defaults, none disables it, custom selects signatureId') gives explicit conditional guidance on which mode to pick per target. There is no naming of alternatives or exclusions, so it stops short of a 5.

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