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

Annotations already declare readOnly=false, openWorld=true, idempotent=false and destructive=false, so the safety profile is covered. The description adds genuine value beyond them: delivery can trigger actions at customer endpoints and 'an accepted message is not proof of delivery,' disclosing the async, side-effecting nature of the call. It does not cover auth requirements or rate limits.

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 sentences, action front-loaded, with zero filler. The prerequisite sentence and the delivery caveat each carry distinct information.

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 mutation tool with no output schema and six undocumented parameters, the description covers the required inputs and the async delivery caveat, which is the most important omission risk. It still leaves messageId, idempotencyKey, and the shape of the untyped payload field unexplained, which an agent needs before invoking.

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% across six parameters, so the description must compensate and only partially does: 'app, recipient, event type, and payload' loosely maps to appId, recipient, type, and the untyped data field. It says nothing about messageId or idempotencyKey, the latter being important given idempotentHint=false.

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 and resource — 'Send a webhook event from an outbound app to the specified customer' — which is clearly distinct from siblings like replay_message, retry_failed_deliveries, and replay_events. An agent can tell this is the fresh-outbound-send tool 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?

There is no when-to-use vs when-not-to-use guidance and no named alternatives, despite close siblings (replay_message, retry_failed_deliveries) where routing matters. The closest thing to guidance is a prerequisite list, which is parameter information rather than selection context.

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