Get authenticated user

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

Annotations already supply readOnlyHint=true, so the safety profile is known. The description adds the crucial OAuth2 token context and implies that the result is tied to the authenticated session, which is behaviorally useful. It does not contradict the annotations and adds value beyond them by clarifying the identity source.

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 two short sentences plus a direct warning. It front-loads the HTTP endpoint and purpose first, then gives usage context, and ends with an actionable caution. No redundant words or filler.

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 zero-parameter, read-only tool with no output schema, the description provides all necessary operational context: what it returns (the current user), when to invoke it, and a critical anti-pattern (don't invent a handle). Nothing an agent needs to call it correctly is missing.

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 zero parameters, the schema is fully covered (100%) and there is nothing for the description to add. The baseline for 0-parameter tools is 4, and the description appropriately avoids inventing parameter details.

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 resource ('the user on this OAuth2 token') and the HTTP verb ('GET'), making it unambiguous. It also distinguishes itself from sibling lookup tools by noting it is the authenticated user, not an arbitrary one, and names the downstream use cases (timeline, likes, bookmarks, mentions).

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?

It explicitly tells the agent when to use this tool ('Call first when you need user id for timeline, likes, bookmarks, or mentions') and warns against fabricating handles ('Never invent a handle'). This effectively routes the agent away from alternative lookup tools without cluttering the description.

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