call_webmcp_tool

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

Behavioral transparency is excellent. The description discloses that interactive tools trigger a native user prompt, that approval can take minutes, that the server sends progress notifications, that a fixed-timeout client may falsely report failure while the tool still runs, and that re-issuing side-effecting calls is dangerous. This goes well beyond the annotations and directly informs safe agent 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 primary purpose in the first sentence. The subsequent sentences are longer but each earns its place by explaining approval latency, progress notifications, timeout failure, and safe recovery behavior. No sentence is filler.

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 generic nature of the tool, the description covers the most important contextual risks: side effects, non-idempotence, approval delays, and timeout handling. It does not describe return values or how to enumerate valid WebMCP tools, but the sibling list_webmcp_tools and the schema's exact-name requirement cover part of that gap.

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 baseline is 3. The description does not add parameter-specific meaning beyond the schema, but it also does not need to: toolName, tabId, and toolArgs are already described adequately in the input schema.

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 opens with a specific verb and resource: "Execute a registered WebMCP tool directly on the target browser tab." This clearly differentiates the tool from siblings like list_webmcp_tools, which only lists available tools, and from browser-control actions like focus_tab or reload_tab.

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 gives clear context for when this tool is invoked and what conditions apply, including interactive approval and timeout behavior. It lacks an explicit "when not to use" statement or named alternative, but the timeout guidance about checking outcomes before re-issuing side-effecting calls provides practical usage direction.

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