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Giancarlo26

obs-action-history

by Giancarlo26

obs_record_chapter

Add a named chapter marker to the active recording for VOD indexing; requires Hybrid MP4 and an active recording.

Instructions

Drop a named chapter marker into the local recording at this instant, so the VOD can be navigated later without anyone scrubbing through six hours of it. This is the cheap version of clipping: it costs nothing, it cannot fail loudly mid-show, and it turns one long recording into something with an index. TRAPS: (1) Recording must be ACTIVE. Streaming is not recording, and a rig can be live for hours with no recording file open at all; in that state this fails with code 501. Check obs_record_control status first. (2) Chapters only exist in Hybrid MP4. Any other container and the marker goes nowhere; OBS 30.2 onward supports no other format for this. The reference machine records hybrid_mp4, so it works here. (3) The marker lands where the recording is NOW, which is the live edge - you cannot chapter something that already happened. Name it for what is starting, not for what just ended.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
chapterNameNoOptional name. Omit and OBS numbers it. Name it for the segment that starts here.
Behavior5/5

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

The description discloses three traps: requires active recording, requires Hybrid MP4 format, and that the marker lands at the current time. Since no annotations are provided, this fully covers behavioral traits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is lengthy but well-structured with a clear opening sentence and a numbered trap list. However, some redundancy exists between the description and the parameter schema text, making it slightly less concise.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers the tool's purpose, usage context, and all failure conditions. No output schema is provided, but the description doesn't need to explain returns since there is none. The traps cover edge cases comprehensively.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema already fully describes the parameter (optional name, omit and OBS numbers it, names the segment that starts). The description adds phrasing about 'starting' vs 'ending' but it is redundant with the schema, providing no new semantic information.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description explicitly states the tool drops a named chapter marker into the local recording at the current instant, with the clear purpose of enabling VOD navigation. It also distinguishes from clipping, which clarifies its role.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It provides explicit guidance on when to use this tool (as a cheaper alternative to clipping) and lists traps that indicate when it cannot be used (inactive recording, wrong format). This gives clear conditions and alternatives.

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

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