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

Goes well beyond the annotations: it discloses the auth scope (manage_campaigns), two concrete failure modes with status codes (409 batch_not_approved, 409 batch_changed after sign-off), and the byte-for-byte send requirement. The gap is that annotations declare readOnlyHint=false and idempotentHint=false while the description never explains what state changes or why repeat calls may differ.

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-loads the applicability condition and the returned payload, then the action instructions, then errors and auth. It is dense but every clause carries information; the first sentence is long enough that it could be split for readability, but nothing is wasted.

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, the description correctly enumerates the return fields, and it covers auth scope and both error paths. It is only incomplete on the mutation/idempotency story implied by readOnlyHint=false and idempotentHint=false, which an agent would need to know before retrying.

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 campaign_id and limit are already documented in the schema, and the description adds no syntax, format, or defaulting detail for either. Baseline 3 applies because the schema does the heavy lifting.

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 verb (returns/reads) and resource (operator-approved signed messages for a relay-identity campaign) and enumerates the payload fields (exact text, recipient, step, evidence link, batch_id, batch_hash). An agent can distinguish this from report_send and list_email_status without opening any schema.

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?

Gives a clear triggering condition ("For a campaign that sends through your own sender (relay identity)") and the mandatory follow-up ("call report_send for every message"), plus the prerequisite that the operator must have signed the batch. It does not explicitly contrast with any sibling as an alternative, so it stops short of full when-not guidance.

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