user_timeline

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

Annotations already declare readOnlyHint=true, so the agent knows it's safe. The description adds valuable behavioral details: returns markdown, newest-first ordering, handle normalization, and include_replies behavior. These go beyond what annotations provide, though it could mention pagination or error conditions.

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 sentences, front-loaded with the core purpose, and adds no fluff. Every sentence contributes useful information, making it highly concise and readable.

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 read tool with an output schema and readOnly annotation, the description covers the essential usage, input flexibility, and return format. It lacks details on pagination or edge cases, but these are likely in the output schema or not critical for basic invocation.

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 description coverage is 0%, so the description must compensate. It explains the username parameter (handle with/without @) and include_replies, but does not mention the limit parameter or its default/max behavior. The limit is somewhat self-evident from the schema, but the description doesn't fully cover all parameters.

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 reads a user's recent posts as markdown, newest first. The verb 'Read' plus the resource 'user's recent posts' is specific, and the format/order details distinguish it from siblings like read_tweet or user_profile.

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 gives clear context for using this tool (reading a user's timeline) and includes practical usage instructions for the username format (with or without @) and the include_replies parameter. It doesn't explicitly mention when not to use it, but the context is clear enough.

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