List images and alt text

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

With no annotations, the description carries the full burden of behavioral disclosure and does so thoroughly: it describes output fields, sanitization of SVG markup, derived flags for missing/overly long alt text, and scoping to top frame and open shadow roots. The agent knows what to expect without needing additional annotation.

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 a single dense sentence with no filler. It front-loads the core purpose and then packs only value-adding details: output fields, flags, and scope limitations. Every clause earns its place.

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 no output schema, the description fully covers what the agent will receive, including specific fields and flags. Combined with the schema's complete parameter documentation, this is sufficient for correct invocation and interpretation of results.

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%, so the schema already documents both parameters. The description adds a bit of behavioral context (e.g., 'Counts always cover every image'), but it does not meaningfully expand on parameter meaning beyond the enum descriptions already present.

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 states a specific verb ('Lists') and a clear resource ('every <img> and inline <svg> on the session page'), and expands on exactly what is returned, including accessible name, source, and derived flags. This clearly separates it from general page-structure tools like get_structure or get_page_snapshot.

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 makes its scope explicit ('Top frame only, open shadow roots only') and the filter parameter clarifies result subsets. It does not explicitly name alternative tools or state when not to use it, but the purpose and limitations are clear enough for an agent to select it appropriately.

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