Run custom ExtendScript inside InDesign to automate document tasks, target a specific open document by name or index, and control actions not covered by built-in tools.
Execute arbitrary ExtendScript code in InDesign
| Name | Required | Description | Default |
|---|---|---|---|
| code | Yes | ||
| document_id | No | Which open document to act on: a name (see document_listOpen) or a 0-based index. Defaults to the front document. |
Changes observed during successful MCP inspections.
v1.6.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. 'Arbitrary ExtendScript code' hints at broad power but does not disclose whether the code runs with full document-mutating privileges, whether it is sandboxed, how errors/exceptions are surfaced, or whether the operation is reversible. For an arbitrary code-execution tool this is a major transparency gap.
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?
A single front-loaded sentence with no wasted words. It is efficient, though for a tool of this complexity the brevity borders on under-specification rather than true conciseness.
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?
There is no output schema and no annotations, so the description must carry the behavioral and return-value burden. It says nothing about what executing the script returns, how failures are reported, or the safety implications of running arbitrary code, leaving the agent under-informed for a high-complexity operation.
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?
Schema description coverage is 50%: 'document_id' is well documented in the schema, but 'code' has no description at all. The description only restates 'ExtendScript code', adding no information about expected syntax, whether results are returned, or how output is captured.
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?
States a specific verb and resource ('Execute arbitrary ExtendScript code in InDesign'), which is far more informative than a tautology. However, it offers no differentiation from the sibling 'script_run', which almost certainly performs a similar or identical function, so an agent cannot tell the two apart.
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?
There is no guidance on when to use this tool versus 'script_run' or any of the many declarative siblings (e.g., text_setContent, image_place) that cover common operations. No preconditions, no mention of whether the document must be open or saved, no exclusion criteria.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.