Look up X user

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

With no annotations, the description carries the full burden. It discloses the return values (user id and DM eligibility) but does not explicitly state read-only behavior, authentication needs, or rate limits. For a lookup tool, the read-only nature is implicit but not explicit.

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 sentences, front-loaded with the purpose, and zero wasted words. Every phrase adds value: the core resolution, the DM eligibility detail, and the usage context.

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 explains what the tool returns (user id and DM eligibility), which is critical given the absence of an output schema. It lacks details on response structure or error cases, but for a simple one-parameter lookup, this is nearly complete.

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 schema already describes the username parameter with 100% coverage (including the leading @ handling). The description adds minimal semantic value beyond the schema, only reinforcing the handle terminology, so the baseline score of 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 tool resolves an X @handle to a user id, and adds the specific capability of determining DM eligibility. This distinct action and resource set it apart from sibling tools like get_x_account or create_dm_draft.

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 explicitly says 'Useful before create_dm_draft,' providing a clear when-to-use context. It also implies this is the tool for handle resolution, distinguishing it from account-level lookups.

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