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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds useful scope context by defining eligibility (messaged the account, still subscribed), but it does not describe pagination or return format beyond the implied contactId.

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?

Two short sentences with zero waste. The purpose and scope are front-loaded, and the follow-on use case is stated immediately without padding.

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 simple read-only list with fully documented optional filters and rich annotations, the description is nearly complete: it defines the audience and explains how the result is used. It does not mention pagination behavior or enumerate returned fields, which is a minor gap given there is no output schema.

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%, and every parameter (tag, limit, search, platform) is already fully described in the input schema. The description adds no additional syntax, format, or filtering detail beyond the schema, so the baseline of 3 is appropriate.

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 uses a specific verb ('List') and precisely defines the resource: contacts a broadcast can reach, who have messaged the account and remain subscribed. It also names the downstream sibling (add_broadcast_recipients), so an agent can tell this apart from list_broadcasts and similar tools.

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 explicitly states the intended use: 'Use this to pick contactId values for add_broadcast_recipients.' That is clear context and names the downstream tool, but it does not list exclusions or alternatives beyond that single workflow.

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