webdev_user_agent

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

Beyond annotations (readOnly, non-destructive, idempotent), description adds that it runs locally, contacts no external service, is rate-limited, and details output flags like isBot, botType, etc. No contradictions.

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?

4-5 sentences, each adding unique value. Front-loaded with purpose, then behavior, then output. No superfluous 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?

Given single parameter and complex output, description adequately explains both input constraints (empty returns 400) and output structure (browser, OS, bot flags). Output schema exists, so not required to list every field, but description covers categories.

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?

Input schema already covers userAgent with description and examples. Description adds context that it parses the value in the request body, not the caller's header, but this is a clarification on usage rather than parameter semantics. Still, it's helpful.

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?

Clearly states it parses a user-agent string into structured browser/engine/OS/device/CPU/feature data and checks for bots. Distinguishes itself from sibling network_request_headers by noting it does not read the caller's own header.

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?

Explicitly explains when to use (when supplying a UA string) and when not to (do not use to read caller's header), and suggests pairing with network_request_headers. Provides clear alternative.

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