webmcp_list_tools

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

No annotations are provided, so the description carries the full burden. It explicitly states 'Side effects: none (read-only state access)' and lists prerequisites. It also mentions the return format: 'Returns: JSON array of available tools with schemas and frame IDs.' This provides adequate transparency for a read-only listing operation.

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 two dense sentences. The core action is stated first, followed by side effects, prerequisites, return type, and usage guidance. No redundant information; 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 the low complexity (1 optional param, read-only), the description covers the essentials: purpose, side effects, prerequisites, and return shape. It does not mention error behavior when no tools are registered or when the feature is disabled, but that is a minor gap for a listing tool. Overall, an agent has sufficient information to call it 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 sole parameter 'instance_id' is fully described in the schema (coverage 100%), with guidance on omitting for the default instance. The tool description does not add any additional parameter semantics beyond what the schema provides, so the baseline score of 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 clearly states 'Lists all WebMCP tools currently registered by the web page.' It specifies the verb (Lists), the resource (WebMCP tools), and the scope (registered by the web page), making it easily distinguishable from siblings like webmcp_invoke_tool or webmcp_list_invocations.

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 provides clear usage context: 'Use this to discover capabilities exposed by websites implementing WebMCP.' It also notes prerequisites (feature enabled, tools registered). It doesn't explicitly contrast with alternatives, but the purpose is obvious; it's the discovery tool while siblings handle invocation or invocation history.

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