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

Annotations already cover readOnlyHint=true and openWorldHint=true, so the description's added value is describing the two-phase simulation (OPTIONS preflight plus the actual request) and the shape of the result ('verdict with reasons'). It doesn't mention rate limits or that the server under test is contacted live, which would complete the picture.

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?

One dense sentence with the core action front-loaded and no filler; every clause (preflight, actual request, returned headers, verdict with reasons) carries distinct information.

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?

With no output schema, the description usefully states what comes back (Access-Control-Allow-* headers and an allowed/blocked verdict with reasons), which is the main thing an agent needs. Minor gaps remain around the method parameter and what a blocked verdict looks like, but the coverage is solid for a 4-parameter diagnostic 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?

Schema coverage is 75% and url, origin, and requestHeaders are already documented in-schema; the description's 'from a given origin' and 'preflight (OPTIONS)' loosely map to the origin and method inputs but add no format or syntax detail. The method enum/default and the custom-header semantics remain explained only by the schema, so the baseline 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?

States a specific verb (simulate/check), the exact resource (browser CORS preflight and actual request) and the output produced (Access-Control-Allow-* headers plus an allowed/blocked verdict). This is easily separable from siblings like check_ssl, scan_security_headers, or trace_redirects.

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 implies when the tool is useful (diagnosing browser cross-origin failures) through 'Simulate a browser CORS preflight', but never states prerequisites, when to prefer it over a sibling, or any exclusions. Usage is inferable rather than explicit.

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