AskEditor

Add timeline marker

add_marker

[write] Drop a ruler marker, optionally labelled. Skipped if one already sits within 120ms. Markers are notes for the person and change nothing in the video. Use to flag beats, cut points or spots to review. Not for captions or on-screen words (use add_caption_line or add_text). Returns the refreshed timeline table, markers (ms, label), tracks and transitions. Related: remove_marker, control_editor.

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": {
      "project_id": "<project_id>"
    },
    "name": "add_marker"
  }
}

Input Schema

Name	Required	Description
`ms`	No	Timeline ms.
`items`	No	Many markers at once, max 60, each with this tool's fields.
`label`	No	Up to 120 characters.
`project_id`	Yes	The AskEditor project this acts on (from list_projects).

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 2, 2026

TDQS

A4.2/5.0

Behavior3/5

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

Annotations already declare non-readonly, non-destructive, non-idempotent. The description adds real value with the 120ms dedupe window and the fact that markers "change nothing in the video" (metadata-only write), plus the return shape. However, the dedupe behavior sits in tension with idempotentHint=false and is not reconciled, and there is no note on permissions or how the 120ms window interacts with batch `items` insertion.

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?

Front-loaded with a [write] tag, then behavior, exclusions, and return values; nearly every sentence earns its place. Mild redundancy between "Markers are notes for the person and change nothing in the video" and the exclusion sentence keeps it from a 5.

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?

With no output schema, the description helpfully names the return payload (timeline table, markers with ms and label, tracks, transitions). Together with the dedupe rule, exclusions, and related tools, an agent has everything needed to call it correctly.

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 coverage is 100%, so the schema documents ms, label (120 chars), items (max 60) and project_id. The description only restates that the label is optional and does not explain how ms or items interact with the dedupe rule. Baseline 3 is correct when the schema carries the parameter burden.

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?

States a specific verb and resource ("Drop a ruler marker, optionally labelled") and explicitly separates itself from add_caption_line/add_text as well as from remove_marker. An agent can distinguish it from every nearby sibling without opening the schema.

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?

Explicit when-to-use ("flag beats, cut points or spots to review") and when-not ("Not for captions or on-screen words (use add_caption_line or add_text)"), naming the alternatives directly. This is the exact routing information an agent needs among ~40 siblings.

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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