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

With annotations covering only readOnly/openWorld, the description goes well beyond them: it discloses the paywall precondition, that arguments are ignored, and the exact failure shape (isError:true with structuredContent {ok:false, error:'PAYWALL', tool, upgrade}). This is exactly the kind of behavioral detail an agent needs to avoid misusing the call.

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 requirement is stated twice (pricing URL, then again as the x-motionspec-key header), and the negative list 'does not compile code, fetch URLs, run an audit or read usage data' is longer than needed. The information is useful but not tightly front-loaded.

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 and minimal annotations, the description carries the full burden and does so: auth requirement, argument behavior, error payload, and a free local fallback are all covered. Nothing material is missing for calling it correctly.

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?

There are zero parameters, so the baseline is 4. The description reinforces this by stating 'Arguments are optional and unused', which confirms the empty schema is intentional rather than truncated.

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 states the actual function plainly: 'This unauthenticated call returns access information only; it does not compile code, fetch URLs, run an audit or read usage data.' That negative framing usefully separates it from siblings motion_audit and motion_compile, but the positive purpose is buried under the paywall preamble rather than stated up front.

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 explicit conditions: requires a Dev Key or Agency plan on the hosted endpoint, reached via the x-motionspec-key header, and it names a concrete alternative ('Read local telemetry for free with npx -p motionspec motion stats'). No sibling tool is offered as an alternative for hosted usage data, so it stops short of full routing guidance.

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