create_subscriber

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

No annotations are present, so the description must fully disclose behavioral traits. It fails to mention crucial behaviors such as whether duplicate emails are rejected or ignored, the default welcome email behavior (hinted at by the parameter but not described), or any authentication/authorization requirements. The tool's side effects on existing data are not addressed.

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?

The description is extremely concise, consisting of a single sentence that conveys the core purpose. There is no wasted text. However, it could be slightly more structured by front-loading the most critical differentiating information (e.g., 'single subscriber'). It is not verbose, but for a tool with multiple siblings, a bit more context would improve it.

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?

Given that there are 3 parameters, no output schema, and no annotations, the description is insufficient for complete understanding. It does not cover error scenarios, rate limits, or the result of a successful addition. The presence of a sibling batch tool and update tool also suggests that more context on when this is appropriate would be valuable. The description leaves significant gaps.

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 input schema has 100% coverage with descriptions for all parameters, so the description does not need to add much. However, it adds no additional meaning beyond the schema. For instance, it does not explain that 'show_id' corresponds to the private podcast ID or that 'skip_welcome_email' defaults to false. Baseline 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 clearly states the action ('Add a subscriber') and the specific context ('to a private podcast'), which is a specific verb+resource. However, it does not distinguish itself from the sibling 'create_subscribers_batch' tool, which also adds subscribers. A more precise description could mention that this adds a single subscriber, differentiating it from the batch operation.

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?

No guidance is provided on when to use this tool versus alternatives like 'create_subscribers_batch' for bulk adds or 'update_subscriber' for modifying an existing subscriber. The agent receives no context on prerequisites or conditions, making it unclear whether duplicate emails are handled or if the subscriber must not already exist.

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