Get a user-agent string

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read operation. The description adds the behavioral nuance that the user-agent should be consistent with the profile's fingerprint, which is useful context. However, it does not disclose additional behavioral traits such as randomness or the handling of the oldUseragent parameter beyond what the schema provides. Thus a 3 is appropriate.

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 action, and every sentence adds value. 'Sample a real user-agent matching a platform and major Chrome version' is the essential purpose, and 'Keep it consistent with the rest of the profile's fingerprint' provides important contextual guidance. No redundant or extraneous content.

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 the tool's simplicity, the description covers the main behavior and adds an important fingerprint-consistency hint. There is no output schema, but the return type (a user-agent string) is clear from the description. The optional oldUseragent parameter is explained in the schema, and the description does not need to repeat it. The main gap is the lack of any mention of what happens if the same user-agent is requested repeatedly, but the schema's description of oldUseragent partially addresses this. Overall, the tool is adequately contextualized.

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 67%, with descriptions for oldUseragent and browser_version, and platform has an enum. The description text reinforces the meaning of platform and browser_version ('matching a platform and major Chrome version') but does not add substantial new meaning beyond the schema. It does not mention the oldUseragent parameter, but the schema already explains it. The overall parameter meaning is sufficiently covered by the schema, so baseline 3 applies.

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 verb 'Sample' and the resource 'a real user-agent', specifying the matching criteria (platform and major Chrome version). It clearly distinguishes this tool from siblings like get_fingerprint, which has a broader scope. The action and purpose are unambiguous.

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 provides implied guidance ('Keep it consistent with the rest of the profile's fingerprint') suggesting it should be used in the context of building a profile fingerprint. However, it does not explicitly state when to use this tool versus alternatives, nor does it mention any exclusions. The usage context is clear but not directive.

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