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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does this thoroughly: it explains the postMessage data-fetching mechanism, states it runs in headless Chromium on the real host surface, records MCP tool calls, and explicitly discloses the fail-closed behavior on browser-mcp outage.

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 dense but every sentence earns its place: it establishes the tool's purpose, explains the failure mode it prevents, describes the execution mechanism, lists the return shape, names the verdict distinctions, and states the fail-closed policy. The key purpose is front-loaded.

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?

There is no output schema, so the description correctly takes responsibility for explaining the return value ({ ok, verdict, visible_text, calls, failures }). It also covers failure modes, timing, and authentication, making the definition complete for an agent deciding whether and how to invoke this tool.

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 already has 100% description coverage for all four parameters, so the baseline is 3. The description does not add parameter-specific meaning beyond the schema, but it does add helpful context about the plugin's MCP calls that relates to the 'expect.tools' assertion.

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 names a specific verb ('PROVE') and resource ('connector ui_plugin actually renders WITH DATA'), and frames it as the required evidence that a UI fix is complete. It also distinguishes its unique outcome categories ('invented tool name' / 'right tool, no data' / 'plugin never asked'), which clearly separates it from generic verify tools.

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 explicit timing guidance ('Run AFTER a UI/data fix'), tells the agent to quote visible_text in its report, and notes that authentication is required. It does not explicitly name alternative tools or state when not to use it, but the context is strong enough to route an agent appropriately.

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