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

The description adds substantial behavioral context beyond the annotations: it clarifies that this tool only PROPOSES a montage for user review (not an actual export), that the user can edit/generate/export later, and that export is free while video generation costs credits. It also details how various parameters affect behavior (trim, generation, speed/mute). With annotations already declaring read-only and idempotent, the description enriches the agent's understanding of the propose-first workflow and cost implications.

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 long but every sentence earns its place. It is front-loaded with the critical scoping statement ('ONLY for video montage...'), then systematically covers exclusions, the proposal workflow, per-item semantics, and cost behavior. The structure flows logically from when-to-use to how-to-invoke, and there is no redundant filler.

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?

The tool is complex (nested MontageItemInput with 13 sub-properties, mixed video/image handling), yet the description covers all major aspects: item types, required fields, trim semantics, duration handling for image vs video, audio generation, aspect ratio, resolution, credit costs, and the post-proposal flow. The absence of an output schema is compensated by explaining the proposal-review-confirm sequence. This is as complete as one could expect for such a tool.

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?

Even though schema coverage is 100%, the description adds meaningfully beyond the schema: it explains how to interpret user requests like '3 seconds each' into setting target_duration: 3 on every item, instructs to tailor per-image motion prompts and avoid generic repeated prompts, and advises inspecting the image with view_image when motion isn't specified. These are practical parameter-usage rules that go beyond the raw field descriptions.

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 sole purpose: video montage/stitching/export workflows, and that it PROPOSES a montage for user review. It explicitly differentiates from sibling tools like propose_brief and mcp_export_montage, and enumerates the exact trigger phrases ('create a montage', 'stitch clips', 'make a reel', etc.). This is a specific verb+resource with strong sibling differentiation.

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 provides explicit when-to-use guidance, including exact user request patterns, and equally explicit when-not-to-use exclusions (photoshoots, lookbooks, product shoots) with the correct alternative path ('request_user_context followed by propose_brief/update_brief'). It also warns against calling the tool merely because images exist in context, and clarifies that photoshoots must first be proposed as a BriefProposal. This is textbook usage guidance.

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