frames_list

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

With no annotations, the description carries the burden. It discloses that only frames the extension can reach are included, which is a behavioral boundary. It also states what output to expect (id and URL), but doesn't explicitly state it's read-only, though that's inferable.

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: the first states the core function and output, the second gives a practical use case. No fluff, information is front-loaded.

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 tool with one optional parameter and no output schema, the description covers purpose, output format, and a use case. It lacks explicit return type details (e.g., array of objects) but provides enough for an agent to understand the result.

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 single parameter tabId is fully described in the schema with default behavior, so the description adds no new information about parameters. It does reference frameId and allFrames:true, but those are for other tools, not this one.

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 lists the tab's frames, including the top document and reachable iframes, with each frame's id and URL. It uses a specific verb 'List' and resource 'frames', distinguishing it from sibling tools which are actions like click or type.

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 when to use it: when a selector doesn't match, the element might be in an iframe, and then to use the result to pass frameId or allFrames:true. This gives a concrete scenario and guidance on how to proceed.

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