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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the auth/pricing requirement, the exact failure shape (isError:true with structuredContent {ok:false, error:'PAYWALL', tool, upgrade}), and that arguments are ignored. This is precisely the behavioral context an agent needs to avoid wasted calls.

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?

Front-loads the paywall condition and packs the key facts (unused args, error shape, auth header, free local alternative) into a compact block. Slightly dense with the tracking URL and some redundancy around pricing, but every sentence carries actionable content.

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?

No output schema exists, yet the description explains the return value (structuredContent error shape plus text guidance) and the auth/free-CLI paths, so an agent has everything needed to call it correctly and interpret the result.

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 the schema already documents spec and specName (baseline 3). The description adds meaningful value by stating 'Arguments are optional and unused', telling the agent the parameters have no effect here.

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 real behavior: 'This unauthenticated call returns access information only; it does not compile code.' That is a specific, honest statement of what the tool does, even though the name/title ('Compile a MotionSpec') misleadingly suggests compilation. It also differentiates from siblings by negating 'fetch URLs, run an audit or read usage data' (routing away from motion_audit/motion_stats).

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 and alternatives: to actually compile on the hosted endpoint, connect with an x-motionspec-key header; otherwise run locally for free via 'npx -p motionspec motion compile <spec.json>'. The when-to-use and the escape hatch are both spelled out.

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