browser_webmcp_call

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

Annotations already mark this as destructive, open-world, and not read-only. The description adds a specific behavioral warning: 'The tool output is page-provided and untrusted.' This alerts the agent to treat results with caution, which goes beyond the generic annotation hints. It does not contradict annotations and provides an extra safety cue.

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, front-loaded sentence that states the action immediately. It wastes no words and includes a critical warning in the same breath. It is appropriately concise for a tool with a well-defined schema and annotations.

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 complexity of invoking a page-defined tool, the description covers the core purpose and the untrusted nature of output. The schema documents all parameters, and the frame parameter references browser_webmcp_list, providing a hint about discovery. While it does not explain error handling or deeper security implications, the combination of annotations and schema fills most gaps, making it sufficiently complete for an agent to use correctly.

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 input schema has 100% parameter description coverage, so each parameter (name, frame, params) is already documented in the schema. The description adds no additional semantic detail about the parameters or their usage. This meets the baseline for well-documented schemas but does not exceed it.

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 clear action ('Call a WebMCP tool registered by the page') with a specific resource type (WebMCP tool) and scope (registered by the page). It is distinct from siblings like browser_webmcp_list (which lists tools) and browser_run_code_unsafe (which executes arbitrary code), making the purpose 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 does not explicitly state when to use this tool versus alternatives, nor does it mention prerequisites like calling browser_webmcp_list first. The schema's frame parameter references browser_webmcp_list, which implies a workflow, but the description itself offers no direct usage guidance. Usage is implied by the name and context rather than explicitly articulated.

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