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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive, so the safety bar is low. The description still adds real context beyond them: 'no tools are called' clarifies it probes the target server without invoking its tools, and the 'free summary; full report is a paid HTTP endpoint' note discloses a commercial gating model the agent otherwise could not know. Missing only rate limits or failure 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?

Two sentences, front-loaded with the verb and resource, then the check list, then the cost caveat — nothing superfluous. The enumeration is dense but every item describes a distinct check the agent gets, so it earns its length.

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?

An output schema exists, so return values need not be described, and the single required parameter is fully documented in the schema. The description covers scope, read-only behavior, and cost, leaving only the failure mode (error vs. a report containing a failing verdict) unstated.

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?

With a single parameter and 100% schema coverage, the schema already explains the url field. The description only adds the qualifier 'streamable HTTP URL', narrowing which endpoint type is accepted, which is marginal but real added meaning. 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?

The description names a specific verb and resource ('Check whether an MCP server ... is usable by AI agents') and enumerates exactly what is inspected: reachability, initialize, tools/list, schema quality score, registry listing, and top fixes. That is far more specific than the title and clearly separates it from the unrelated sibling x402_status_leaderboard.

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?

Usage is implied by the purpose (validate a candidate MCP endpoint before relying on it), and the free-vs-paid note sets expectations. But there is no explicit when-to-use / when-not guidance and no alternatives named; the only sibling is unrelated, so no routing is needed, but the description never states prerequisites either.

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