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Excalidraw · Holon

by io.github.holon-sh
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put_image

Idempotent

For the board's page: store the file of an image on the board, as a data URL.

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": {
      "board": "<board>",
      "id": "<id>",
      "dataURL": "<dataURL>"
    },
    "name": "put_image"
  }
}

Input Schema

NameRequiredDescriptionDefault
idYesThe fileId of the image's Excalidraw element.
boardYesThe board's id, as in its URL.
dataURLYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

C2.9/5.0
Behavior2/5

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

Annotations already declare idempotentHint=true and destructiveHint=false, so safety is covered. The description adds nothing beyond what the name implies: it does not state whether an existing image is overwritten, whether the target element must pre-exist, the practical size limit, or any failure modes. With annotations carrying the safety profile, this still leaves real behavioral questions unanswered.

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?

A single short sentence with no wasted words, and the target ('For the board's page') is front-loaded before the action. It is efficient, though the terseness is part of why prerequisites go unstated.

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

Completeness3/5

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

The tool is simple (three required scalar parameters, an output schema exists, no nesting), so minimal prose is defensible. However, the description omits the prerequisite relationship between 'id' and an existing image element and any overwrite/replace semantics, which an agent needs 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 67%: board and id are documented in the schema, while dataURL is described only by a regex pattern. The description's phrase 'as a data URL' adds a small amount of meaning for that undocumented parameter, but gives no encoding, size, or format guidance. Baseline 3 fits since the schema does most of the work.

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 states a specific verb and resource ('store the file of an image on the board') and adds the storage representation ('as a data URL'), which distinguishes it from the retrieval sibling get_image. It does not explicitly contrast with any sibling, but the action is unambiguous.

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?

It never says when to call this versus get_image, draw, or sync, nor what precondition must hold (e.g. that the Excalidraw element identified by 'id' must already exist). No exclusions or ordering guidance are given; the agent must infer usage entirely from the name.

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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