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

Annotations already mark this as destructive/non-read-only, and the description adds meaningful context: 'Effect: external-email' explains the side effect, permissions are listed, and retry behavior via idempotency_key is disclosed. This goes beyond the structured annotation fields without contradicting them.

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 dense but every sentence earns its place: purpose, prerequisite, parameter guidance, external effect, retry guidance, permissions, and API reference. It is front-loaded with the core action and contains no filler.

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 the output schema and annotations, the description covers the essential context: prerequisite broadcast state, subscriber lookup path, recipient flexibility, idempotency, permissions, and external side effect. It is complete for an agent to select and invoke this tool correctly.

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 the baseline is 3. The description adds extra meaning by explaining that the recipient need not match the saved Subscriber, that subscriber_id drives personalization, and that idempotency_key enables safe retry. This is genuinely useful beyond the schema.

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 opens with a specific verb and resource: 'Sends a test message from an existing Broadcast.' It clearly distinguishes this from broadcasts_send (actual send) and from automations_send_test/sequences_send_test by scoping to Broadcast and test delivery.

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?

It provides clear context: use an existing Broadcast with an email delivery connection, use subscribers_list to find a Subscriber ID, and the recipient can be any test inbox. It does not explicitly state when not to use it or name alternatives, but the test-vs-send distinction is implied by the sibling tools.

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