List frames

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

Annotations already declare readOnlyHint=true, and the description adds significant behavioral context: Chrome's accessibility tree stops at frame boundaries, querySelector never crosses them, and index 0 is always the main frame. It also explains how results should be consumed by other tools. This goes well beyond the annotations and meaningfully clarifies tool behavior.

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 front-loaded with the core action and purpose, then provides a brief but necessary explanation of the frame boundary problem, and closes with concrete usage instructions. Every sentence contributes value; there is no filler or repetition of the title or schema.

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 read-only listing tool with a single optional parameter and an output schema, the description is complete: it explains why the tool exists, when to use it, what the output means (index 0 main frame), and how to use the result with related tools. Nothing necessary for correct invocation 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?

Schema description coverage is 100%, and the only parameter, browser, is fully documented in the input schema with its own description. The tool description does not add parameter-level detail, which is fine because the schema already carries the full burden. 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 starts with a specific verb and resource: 'List the page's frames'. It then explains the purpose: making frame content reachable, which distinguishes this tool from take_snapshot and query_selector, which operate only on the main frame. The clear framing of iframe content as otherwise invisible gives the tool a precise identity.

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 explicitly explains when to use list_frames: whenever content lives inside an iframe and is invisible to take_snapshot and query_selector. It names the alternative tools that accept the resulting frame index or id, and states that index 0 is always the main frame. This gives the agent a complete routing decision without further inference.

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