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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it uses a real mainland-China egress and reports HTTP status, latency, and DNS resolution, which goes beyond the annotations. No contradiction is present.

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, well-structured sentence that front-loads the core action and outputs, followed by a clear purpose statement. It contains no filler or redundant phrases; every segment contributes to understanding the tool.

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 an output schema available, return values need not be described. The description covers purpose, measurement method (real China egress), outputs (HTTP status, latency, DNS), and the primary use case. Minor caveats or interpretation guidance could enhance completeness, but the current context is sufficient for the tool's simplicity.

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 schema describes the only parameter 'url' as a 'Full URL to test, e.g. https://example.com', providing complete coverage. The description reinforces the URL's role but does not add new parameter-level semantics beyond what the schema already states, so the baseline score of 3 is appropriate.

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: 'Fetch a URL from a real mainland-China network egress and report HTTP status, latency and China DNS resolution.' It clearly states the tool's purpose and distinguishes it from siblings by focusing on China-specific reachability, which no other sibling tool addresses.

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 explicitly frames the tool as answering 'is my site/API usable from China?' and notes 'you cannot get this from a VPS abroad,' which indicates the intended use case. It does not name alternative tools, but the context clearly implies when this tool is appropriate relative to other network-checking tools.

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