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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely new behavioral facts not present in annotations: the exact GET route and the $0.10 price per call, which matters for cost-aware tool selection. It stops short of describing the first-call 402 challenge flow or rate limits, but the schema's payment field covers that.

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?

A single compact sentence with the purpose front-loaded and the price/route trailing, so nothing is wasted. It is arguably too compressed given the complexity of the x402 payment flow, but there is no filler or repetition.

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?

For a 2-parameter, no-output-schema tool with annotations present, the description covers what the tool returns at a high level (pass/fail). It omits what 'WebMCP agent-compatibility' actually inspects and how its result should route an agent to order_webmcp_upgrade, which leaves a real gap in a crowded check_* / webmcp_* sibling set.

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 description coverage is 100%, so both the 'host' and 'payment' parameters are already documented in detail, including the nuance of omitting payment on a first call. The description's '?host=' fragment confirms host is a query parameter but adds no semantics beyond the schema; 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 and resource ('WebMCP agent-compatibility check') plus the outcome shape ('pass/fail verdict'), which is more than a restated name. It does not, however, distinguish itself from near-siblings like check_x402, lint_protocol_card, or order_webmcp_upgrade, leaving the agent to infer the boundary.

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 contains no when-to-use or when-not-to-use guidance and never names the alternative tools (e.g. order_webmcp_upgrade for remediation, lint_protocol_card for protocol validation). The only procedural hint — omit payment on a first call to receive a 402 challenge — lives in the schema, not the description.

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