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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds nothing beyond that – no note on permissions, error behavior for an unknown subscriber, or whether membership must exist – so it contributes no behavioral context of its own.

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?

A single short sentence with zero waste and the resource stated up front. It is efficient, though the brevity reflects under-specification rather than disciplined compression.

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 two-parameter read with full schema coverage and complete annotations, the definition is minimally sufficient. Still missing is any hint of the return payload (subscriber fields) or the failure mode when the subscriber is not in the audience, which would matter to an agent deciding whether to call this or list.

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%, with both 'id' (Audience ID) and 'subscriber_id' (Subscriber ID) documented inline, so the baseline is 3. The description's phrase 'subscriber of an audience' loosely maps to the two-parameter scoping but adds no format, validation, or lookup 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?

The description names a specific verb ('Retrieve') and resource ('one subscriber of an audience'), and 'one' distinguishes it from the list-audience-subscribers sibling. However, it does not distinguish this from other single-resource getters such as get-contact, nor does it name the sibling it is not, so the agent must infer the boundary.

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?

There is no statement of when to use this tool versus list-audience-subscribers, get-contact, or update-audience-subscriber. The agent must infer usage entirely from the name and the presence of an 'id' + 'subscriber_id' pair.

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