twitter_user_by_username

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the bar for transparency is lower. The description adds valuable context by specifying the exact return structure (fields and nested public_metrics), providing an example, and noting the auth requirement (X_BEARER_TOKEN). It does not mention error conditions or rate limits, but for a simple read-only lookup with good annotations, this is reasonably transparent.

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 and front-loaded with the core purpose. It includes the return shape, an example, and auth note in just a few lines with no filler. Every sentence contributes useful information.

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 lookup tool with 2 params and no output schema, the description is fairly complete: it explains the input format, return fields, and auth. However, it does not clarify how this tool differs from sibling Twitter tools (e.g., whether 'twitter_user' uses an ID, or 'twitter_users_by_usernames' handles multiple accounts), which could lead to agent confusion in a large tool 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 coverage is 100% and both parameters have descriptions in the schema. The description's 'without the @' and example are already covered by the schema's param description ('Handle without the @ (e.g. NBA, AFL, wojespn)'). The description adds no new meaning for the parameters, so 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 states a specific verb+resource: 'One account's public profile by @handle'. It clearly indicates this tool fetches a single user's profile. However, it does not explicitly distinguish itself from sibling tools like 'twitter_user' (likely by ID) or 'twitter_users_by_usernames' (plural), so it lacks explicit sibling differentiation.

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 implies usage when you have a @handle for a single account, but provides no explicit when-to-use vs alternatives, no exclusions, and no mention of when to prefer 'twitter_users_by_usernames' for multiple accounts or 'twitter_user' for ID-based lookups. It gives a usage example and auth note, but no strategic guidance.

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