timeline_frame

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

With no annotations, the description carries the full behavioral burden, and it does well: it discloses the auto fallback chain, that source fallback excludes timeline transforms, grades, Fusion and overlays, and that mode='composite' fails explicitly when a true still is unavailable. These non-obvious behaviors are exactly what an agent needs to interpret the returned image correctly.

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 purpose, followed by three sentences of high-signal fallback and failure behavior. Every sentence earns its place with no repetition or 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 mode behavior and fallback limitations are covered well, and an output schema exists so return format need not be described. However, with five optional parameters and no schema descriptions, the description leaves open important invocation details: the expected timecode format, whether frame and timecode are mutually exclusive, and what happens when neither is supplied.

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. It adds meaningful semantics for mode ('auto' vs 'composite') and clarifies that frame/timecode refer to absolute positions. However, it does not explain format, max_width, or how frame and timecode interact when both or neither are provided.

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 returns 'a native MCP image' for an 'absolute timeline frame or timecode', which is a specific verb and resource. It does not explicitly differentiate from siblings like preview_timeline, but the frame/timecode targeting and 'native MCP image' output make the purpose reasonably distinct.

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 usage: request a still for a specific absolute timeline frame or timecode, with 'auto' mode attempting composite first. However, it provides no guidance on when to prefer this over related siblings such as preview_timeline or set_playhead, and no explicit exclusions or alternative routing.

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