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

Annotations only say readOnlyHint=false and destructiveHint=false; the description adds genuine context beyond that — that this dispatches a real outbound email, that it is gated on delivery configuration, and how to make retries safe. It still omits failure modes and whether repeated submissions with new keys create duplicates.

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?

One compact sentence with a semicolon clause: the action, the availability constraint, and the retry rule are all front-loaded with zero filler. Nothing could be removed without losing 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?

With a full output schema present, return values need not be explained, and 100% schema coverage handles parameters. The description supplies the two things structured fields cannot: the external side effect and the configuration precondition. It could still say how an agent detects the unconfigured state, but it is otherwise adequate.

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 100%, so all six parameters including the idempotencyKey pattern and retry semantics are already documented in the schema. The description's idempotency sentence duplicates what the idempotencyKey schema description already says, adding no new parameter meaning. Baseline 3 applies.

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 ('Submit a real email inquiry') and makes the side-effecting nature unmistakable, which naturally distinguishes it from the twelve read-only sibling tools. It stops short of explicitly contrasting itself with any named alternative, but the purpose is unambiguous.

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 real precondition ('unavailable until delivery is configured') and explicit retry guidance ('Reuse idempotencyKey for retries'), which is more than most tools offer. It does not name when to prefer another tool or state hard exclusions beyond the configuration gate.

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