Add timecode overlay

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

The description adds substantial behavioral detail beyond the annotations: the timecode is live and re-evaluates every frame, count_down clamps at zero, FPS is probed live with a fallback, and the chain ends in a Null TOP 'out'. It does not contradict the annotations and clearly indicates the tool builds a node chain (consistent with readOnlyHint=false).

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 dense but every sentence earns its place: implementation approach, mode semantics, formatter location, live FPS probing, sibling distinction, and output terminal. No wasted words. The structure flows from general action to mode details to implementation specifics.

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 complexity (8 parameters, no output schema, open-world behavior), the description covers everything needed: what it builds, how timecode computation behaves, what the output is ('Null TOP out'), and how it differs from sync_timecode. The schema handles parameter syntax, and the description fills in behavioral context.

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 coverage is 100%, so the baseline is 3, but the description enriches several parameters: it clarifies that 'clock' shows time since project start and is 'NOT the OS wall clock,' that count_up starts from zero when the overlay is built, and that count_down clamps at 00:00:00:00. These are semantic clarifications not present in 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 opens with a specific verb and resource: 'Overlay a running HH:MM:SS:FF timecode (or a countdown) onto an input TOP as VISUAL pixels.' It immediately distinguishes itself from sync_timecode, which is a sibling tool for syncing clock signals rather than rendering pixels. This leaves no ambiguity about what the tool does.

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?

It explicitly names the closest alternative (sync_timecode) and explains the difference: 'Distinct from sync_timecode, which syncs a CLOCK SIGNAL (no pixels) — this tool draws the timecode into the image.' The mode breakdown (clock/count_up/count_down) also clarifies when each mode should be used.

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