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

Annotations already indicate this is a write/destructive operation (destructiveHint=true), and the description supplements that with an auth requirement. It does not disclose side effects, idempotency, or whether an existing subscription is replaced, but the annotation covers the mutation warning.

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, no filler. The core constraint 'exactly one' is placed first, and the auth requirement is a useful second sentence. Every word earns its place.

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?

The description covers the main inputs and authentication, but it does not explain subscription behavior, how tags or entity_ids are discovered, whether subscriptions can be overwritten, or what the response contains. For a destructive/write tool with no output schema, slightly more context would be helpful.

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?

The description adds crucial meaning beyond the schema by stating the mutually exclusive selection: exactly one of topic, tag, or entity_id. Schema coverage is low, especially for tag and entity_id, so this explicit constraint is valuable.

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 states a specific action ('Subscribe') and clearly defines the target resource: exactly one topic, tag, or entity_id. This differentiates it from the many sibling tools by saying precisely what it operates on.

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?

The description implicitly tells an agent when to use it: when subscribing to a topic, tag, or entity_id is needed. It also adds the auth prerequisite ('Requires an agent bearer key'), but it does not explicitly contrast with alternative tools or explain when not to use it.

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