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

There are no annotations, so the description carries the full burden of disclosure. It mentions billing per call (1 credit) and lists the output fields, but does not disclose whether the operation is read-only, requires authentication, or has side effects. Critically, it says 'provide only the userId' while the schema allows a username alternative that overrides the userId, making the description misleading about accepted inputs. This lack of clarity around input handling and side effects lowers transparency.

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 compact (two sentences) and front-loaded with the core purpose. Including billing and group info is minor but not excessive. It avoids redundancy, though the second sentence repeats 'followings'; this is acceptable. Overall, it's efficient for a simple tool.

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 tool has no output schema, so the description appropriately lists the returned fields (id, username, createdDate, followings, followers). However, it omits essential context such as pagination behavior, any rate limits (apart from billing), authentication requirements, and clarifies the username override. The presence of sibling tools with different scopes further necessitates a clearer explanation of what 'basic' means. Given the simple nature of the endpoint, the description is adequate but leaves notable gaps, especially around input alternatives and potential limitations.

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?

With schema description coverage at 50%, the description needed to compensate for the undocumented userId parameter, but it only repeats 'provide only the userId' without adding meaning (e.g., format, example, or that it's a numeric string). Meanwhile, it contradicts the schema's optional username parameter. The list of output fields adds some context but not input semantics. The tool description fails to clarify the relationship between userId and username, leaving the agent confused.

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 tool's purpose: returning a basic list of a user's followings, and lists the fields returned. It distinguishes itself from sibling tools by using 'basic' (vs. the likely more detailed get_user_userId_followings and IDs-only get_user_userId_followings_ids), though it doesn't explicitly name those alternatives. The verb and resource are specific and clear.

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 provides no guidance on when to use this tool versus the sibling followings endpoints. It only instructs to provide the userId, which is a usage instruction, not a selection criterion. No mention of when to prefer 'basic' over 'full' or 'ids' is given, leaving the agent to guess based on the title and context.

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