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

Beyond the annotations (readOnlyHint true, openWorldHint false), the description discloses the paid-plan requirement, the exact failure payload (isError:true, structuredContent {ok:false, error:'PAYWALL', tool, upgrade}), and that arguments are optional and unused. That is unusually rich behavioral context an agent could not infer from structured fields.

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 paywall/auth constraint is front-loaded and the sentences are dense but purposeful, covering behavior, return shape, and the local alternative. The negative enumeration is slightly padded, keeping it from a perfect score.

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, yet the description fully specifies the return payload, the auth prerequisite, and the fallback path. Nothing an agent needs to call this correctly or interpret its failure is missing.

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 100%, so the baseline is 3, and the description adds real meaning by stating 'Arguments are optional and unused' — clarifying that the documented url parameter is effectively ignored. It stops short of 5 because this note somewhat conflicts with the schema's own claim that url is 'The page URL to audit'.

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 explicitly states the tool's real behavior: 'This unauthenticated call returns access information only; it does not compile code, fetch URLs, run an audit or read usage data.' That negative enumeration also distinguishes it from siblings like motion_compile and motion_validate. It loses a point because the name/title promise an audit while the description says no audit occurs, which is an unusual and potentially confusing framing rather than a clean verb+resource statement.

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?

It gives clear preconditions (Dev Key or Agency plan, x-motionspec-key header) and an explicit free alternative ('npx -p motionspec motion audit <url> --json'). It does not, however, explain when to prefer this tool over the sibling tools, so it falls short of a full 5.

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