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

readOnlyHint=true already establishes this as a safe read, and the description's 'handle to remove them' is best read as pointing at a sibling mutation rather than claiming a write — but that ambiguity is exactly the kind of thing a description should resolve. Nothing is said about result size, ordering, or whether pagination applies when many viewers are present.

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 no padding, and the subject ('Everyone who opened your broadcast') is front-loaded. The only wasted ambiguity is in the 'handle to remove them' clause.

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 no output schema, no parameter documentation, and only a minimal readOnlyHint annotation, the description needs to do more. It never describes the shape of a viewer entry, what the 'handle' looks like, or how the id/key are obtained — the main things needed to call and use this 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 description coverage is 0%, so both required parameters are undocumented in the schema and the description must compensate. It only says 'Needs its id and key' without clarifying that id is the broadcast id versus a viewer id, or what 'key' is (auth credential? broadcast key?), leaving the agent to guess.

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 core function is inferable: it returns the list of viewers who opened your broadcast. However, the trailing clause 'with a handle to remove them' muddies whether this tool itself removes viewers or merely returns an identifier for remove_viewer, and 'its id' never names what the id belongs to.

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?

Mentioning 'a handle to remove them' implicitly routes the agent toward remove_viewer, but there is no explicit when-to-use, when-not, or statement of the relationship to siblings like my_broadcasts or live_streams. Usage must be inferred.

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