timeline_add_marker

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

No annotations are present, so the description carries the full burden. It states the mutation ('Add a marker') but does not disclose prerequisites (e.g., an open timeline), whether markers can overwrite existing ones, side effects on the timeline, or what the return value indicates. Minimal behavioral insight beyond the raw action.

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?

Exactly one sentence with no fluff. It front-loads the core action and target, and all parameter details are left to the schema, making it appropriately concise.

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 tool is a straightforward mutation with six fully-documented parameters and an output schema. However, with no annotations and a terse description, it lacks context about the 'current timeline' requirement, differentiation from clip/item marker tools, and any prerequisites. For a tool with moderate complexity and many marker-related siblings, this is minimally adequate.

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 fully documents all six parameters with descriptions (100% coverage), so the description does not need to repeat them. The phrase 'at a specific frame' aligns with frame_id but adds no additional semantics. Baseline of 3 is appropriate given the schema coverage.

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 (add), the resource (marker), the target (current timeline), and the location constraint (at a specific frame). It effectively distinguishes itself from sibling tools like clip_add_marker and item_add_marker by specifying 'current timeline'.

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 usage—when a timeline marker is needed at a specific frame—but provides no explicit guidance on when to use this tool versus clip_add_marker or item_add_marker, nor any exclusions. It lacks explicit alternatives or when-not-to-use scenarios.

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