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

Annotations provide only readOnlyHint=false and destructiveHint=false, so the description carries the burden. It discloses that the call 'replacing the current programme' (a mutation) but assures 'Every earlier EDL version remains recoverable' and 'it never creates an invalid empty timeline.' It also notes the atomic append-only write. This goes beyond annotations and sets expectations for side effects and safety.

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 longer than average but every sentence earns its place: scoping note, purpose, usage trigger, safety guarantee, recoverability, and parameter hints. It is front-loaded with the critical 'PROJECT-SCOPED' and the core action, and it avoids fluff.

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 tool with 7 parameters and no output schema, the description covers the core purpose, usage context, and some parameter semantics, but it omits details like the exact return format (only 'returns the project identity with its result'), error conditions, and prerequisites beyond project_id (which is in schema). It is adequate but not exhaustive for a complex mutation.

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 low (29%), so the description must compensate. It does add meaning for duration_s and clip_start_s ('select a video window') and references motion/fit to insert_media for consistency. However, it does not explain asset_key (though implied by 'uploaded video clip or image') or motion_motif beyond the schema's own description. It partially fills the gap but not fully.

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 action: 'Start a NEW media-only sequence from one uploaded video clip or image, replacing the current programme in ONE valid append-only EDL write.' It clearly identifies the resource (a media sequence) and distinguishes it from the project's main video, and names the sibling 'insert_media' for later scenes, so an agent can differentiate it without opening schemas.

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 gives an explicit usage condition: 'Use this when the requested story should be assembled from uploaded assets instead of the project's main video.' It also positions it as 'the safe first operation in an atomic recipe' and points to insert_media for later scenes. It lacks an explicit 'when not to use' but the context is clear and actionable.

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