MotionSpec — web animation accessibility MCP

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: it is a bootstrap/discovery call that returns definitions rather than performing work, and it discloses that motion_compile requires the CLI or a hosted key.

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-loaded with what is returned, then the call order, then the compile caveat. The trailing promotional URLs (motion-check, pricing) are useful pointers but slightly dilute the definition; the substance is still tight and well ordered.

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, the description compensates by enumerating the return contents (names, purpose, schemas, defaults) and the authoring rules. Combined with the sequencing guidance and the compile auth caveat, an agent has everything needed to use it correctly in the workflow.

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?

The tool takes zero parameters, so there is nothing for the description to document and the baseline of 4 applies. The description correctly implies no input is needed to retrieve the catalog.

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 (returns) and resource (the catalog of verified motion primitives) and enumerates the payload (names, purpose, parameter schemas, defaults) plus the authoring rules for a MotionSpec. It also implicitly distinguishes itself from siblings by naming motion_validate and motion_compile as downstream steps.

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?

Gives an explicit sequencing instruction ('Call this FIRST, then write the spec yourself and validate it with motion_validate') and clarifies where motion_compile actually runs (CLI or hosted endpoint with a key). An agent knows both when to call it and which sibling to use next.

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

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

The description goes well beyond the readOnlyHint and openWorldHint annotations by disclosing fail-closed behavior, the exact return shape, and the non-obvious fact that warnings can be non-empty while ok=true. It also explains the accessibility implication, which is critical for correct agent 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?

The description is compact and front-loaded, with the core validation behavior stated first, followed by the return shape and the critical warning caveat. Every sentence earns its place, and the formatting highlights the most important behavioral nuance.

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 single-parameter, read-only validation tool with no output schema, the description fully covers what the tool does, when to use it, what it returns, and the key failure and warning semantics. An agent has sufficient information to select and invoke it correctly without additional context.

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 for the single parameter is 100%, so the baseline is 3. The description adds meaningful semantics by clarifying that the spec parameter is a MotionSpec and by enumerating the validation dimensions applied to it, such as the primitive allow-list and injection rules, which the schema alone does not convey.

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 a specific verb ('Checks') and a specific resource ('MotionSpec'), then enumerates exactly what it validates against: schema, primitive allow-list, parameter bounds, and injection rules. It clearly distinguishes itself from the sibling motion_compile by positioning validation as a pre-compile safety check.

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 explicitly says 'Use to pre-check a spec before compiling,' which gives clear guidance on when to call this tool. It also explains the important warning behavior so an agent knows this is the right tool for accessibility checks before compilation, though it does not explicitly name or exclude alternatives beyond the pre-compile framing.

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