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

Annotations already declare the write/idempotency/destructive profile, and the description adds two things they cannot: a draft-only mutation constraint and a `full_access` API key requirement. It omits whether the update is partial or a full replacement of omitted fields, which matters for a PATCH on a mutable draft.

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?

Short and front-loaded with the core action, but "only drafts can be updated" appears twice in consecutive sentences, which is pure waste. The trailing API/operationId metadata is defensible for traceability but consumes a third of the text.

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 9-parameter mutation with no output schema and near-zero schema coverage, the description supplies auth and lifecycle constraints but leaves the field-level contract largely unstated. It is enough to avoid calling it on a sent broadcast, not enough to fill the body confidently.

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 only 11% — just `from` and `reply_to` carry descriptions — across 9 parameters. The phrase "any field of the create request" defers entirely to a sibling tool's schema and explains nothing about `id`, `audience_id`, `subject`, `html`, `text`, `name`, or `preview_text`, leaving most parameters undocumented in both places.

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?

Specific verb plus resource ("Update a broadcast") with an added scope qualifier that only drafts are mutable. It does not explicitly contrast itself with create_broadcast, delete_broadcast, or send_broadcast, so the agent must infer the boundary from the sibling list.

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?

"Only drafts can be updated" is a concrete precondition/exclusion that tells the agent when this tool will fail, which is more than most definitions provide. It stops short of naming an alternative path for already-sent broadcasts, so the agent gets a constraint but no routing guidance.

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