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

Adds real behavioral context beyond annotations: recipients can only be ADDED, removal is impossible, and trimming a draft requires deleting it and starting over. This irreversibility warning is critical and not captured by the idempotentHint/destructiveHint flags. It also confirms that adding does not send, which is not stated elsewhere.

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 short sentences, front-loaded with the primary action and its most important constraint (irreversibility). Every sentence carries distinct, useful information with no waste.

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 draft-mutation tool with no output schema, the description covers the essential behavioral traits: dual read/write modes, the no-removal limitation, and that nothing is sent. Minor gaps remain (e.g., no explicit return shape), but these are not required given the schema coverage and annotations.

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 the schema already documents broadcastId, contactIds (max 500, from list_broadcast_contacts) and populate. The description reinforces the read-mode semantics of omitting both params but adds little syntax or format detail 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?

States a specific verb (add) and resource (broadcast recipients), and explicitly clarifies the write-vs-read duality, distinguishing it from send_broadcast ('Adding still sends nothing'). An agent can tell exactly what this does relative to siblings like list_broadcast_contacts and send_broadcast.

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 clear context for both modes: call with neither contactIds nor populate to read, otherwise it adds. It explains the intent of each parameter but does not explicitly name alternative tools or exclusions beyond the read/add split.

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