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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description need not restate safety. It adds value by describing the planning behavior—returning brief, open questions, characters, model slug, prompt draft—and the special split behavior for long videos. No contradiction with annotations.

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?

Two sentences, front-loaded with the most important instruction ('Call FIRST'), and each clause adds unique value: what the plan includes, and what happens for long videos. No wasted words or restatement of the name.

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?

Given the tool's planning role and no output schema, the description adequately conveys the return structure and the long-video exception. It is slightly incomplete in that it doesn't tell the agent what to do with the plan afterward (e.g., feed the prompt draft into magnific_video_generate), but for a read-only planning tool with rich return details, it is reasonably complete.

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 0%, so the description must compensate, but it only indirectly references prompt and duration ('Videos >15s'). It does not explain styleHint, aspectRatioHint, referenceIdentifiers, or how durationHint should be formatted. The property names are somewhat self-explanatory, but the description adds minimal semantic value beyond the schema.

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 clearly states the tool's role: 'Call FIRST for any video request' and explains it returns a markdown plan with concrete sections. This distinguishes it from siblings like magnific_video_generate and magnific_video_concatenate by establishing it as the planning step, not the execution step.

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 instruction 'Call FIRST for any video request' is explicit and unambiguous about when to use this tool. It also provides conditional guidance for videos over 15 seconds, directing the agent toward video_concatenate. However, it does not explicitly name when-not-to-use alternatives or state that this tool should not be used to directly generate video.

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