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

Annotations indicate the tool is a non-destructive, non-idempotent write operation. The description adds no behavioral context beyond restating the action; it does not clarify side effects, prerequisites, duplication behavior, or what happens to existing clips. For a mutation operation, the description should disclose core behavioral traits (e.g., whether it inserts without replacement, whether assets/projects must exist), but it remains a near-tautology of the schema and title. This adds marginal value over the 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?

The description is a single, compact sentence that begins with the core action and object, then adds a clarifying scope note ('including B-roll and static images'). There is no filler, repetition, or unnecessary detail. The structure is front-loaded and appropriately sized for a tool of this complexity.

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?

Despite having 9 parameters with enums (placementIntent, positionPreset, animationPreset) and an output schema, the description offers no higher-level guidance on parameter selection. It does not explain when to use layerIndex versus placementIntent, when durationSeconds is needed, or how options like positionPreset affect output. The schema covers syntax, but the description fails to provide the contextual decision-making help an agent needs to invoke the tool effectively. For a complex tool, this is insufficient.

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 input schema provides 100% description coverage for all 9 parameters, including detailed descriptions for each. The tool description does not add any additional semantic meaning beyond what is already in the schema—it focuses only on the general action. Since the schema covers parameter meaning and defaults, the description's lack of parameter elaboration is acceptable, hitting the baseline of 3.

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 action (place) and resource (image or video asset onto a BlitzReels project timeline), with an explicit mention of B-roll and static images. This distinguishes it from sibling tools like timeline_audio_add, add_text_overlay, and add_transition, which serve different media types. The verb and target are unambiguous, making the purpose immediately clear to an agent.

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 implies the primary use case—adding media to a timeline—but does not explicitly contrast it with alternatives or mention when not to use it. It does not reference sibling tools or state conditions like 'for text use add_text_overlay.' The mention of 'including B-roll and static images' hints at scope but lacks exclusion or alternative routing. This is adequate but leaves the agent to infer when this is the correct choice.

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