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add-marker

Place a marker on an After Effects layer or composition at a specified time, with optional comment, label color, chapter, URL, and duration.

Instructions

Add a marker to a layer or composition at a specified time. Markers can include a comment, label color, chapter name, URL and duration.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "compIndex": "<compIndex>"
    },
    "name": "add-marker"
  }
}

Input Schema

Name	Required	Description
`url`	No	URL to open when the marker is reached (for web export).
`label`	No	Label color index (0 = none, 1-16 map to AE label colors).
`chapter`	No	Chapter name associated with the marker.
`comment`	No	Marker comment / label text.
`duration`	No	Marker duration in seconds (0 = point marker).
`compIndex`	Yes	1-based composition index.
`layerName`	No	Target layer name (alternative to layerIndex).
`layerIndex`	No	Target layer index (required for layer markers).
`markerType`	No	'layer' (default) or 'comp' for a composition marker.
`timeInSeconds`	No	Time in seconds where the marker is placed. Defaults to current time.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Oct 17, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden. It mentions marker attributes but fails to disclose behaviors like the default time (current time), default marker type ('layer'), or potential side effects (e.g., modifying the composition). For a mutation tool, this is insufficient.

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

Conciseness5/5

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

The description is two concise sentences, front-loaded with the action and target, and contains no unnecessary words. Every sentence contributes meaning.

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

Completeness2/5

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

This tool has 10 parameters, no output schema, and no annotations, yet the description provides minimal context. It does not explain required parameters (compIndex), the distinction between layer and composition markers, or how it differs from the sibling add-markers-bulk. The complexity demands more than this.

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?

Schema description coverage is 100%, so the schema already documents all 10 parameters. The description adds marginal value by listing the marker attributes (comment, label color, chapter, URL, duration) but does not explain parameter relationships or defaults beyond the schema.

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

Purpose4/5

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

The description clearly states 'Add a marker to a layer or composition at a specified time' with a specific verb and resource, and lists what markers can include. However, it does not explicitly distinguish from the sibling tool add-markers-bulk, which is very similar.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus alternatives, no mention of prerequisites, and no exclusions. The description simply states what it does without providing usage context.

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