remotion-dev/remotion · error · Error

compositionName must be a string.

Error message

compositionName must be a string.

What it means

The Studio Web MCP selectComposition tool could not find a composition whose id equals the provided compositionName in the currently loaded compositions.

Solutions

1. List available compositions first via the MCP listing tool and use an exact id
2. Ensure the target composition exists in src/Root.tsx and Studio has reloaded
3. Retry after compositions finish loading in Studio

const ids = compositionsRef.current.map((c) => c.id);
if (!ids.includes(compositionName)) { /* list valid ids to the caller */ }

try { await tool.execute({compositionName}); } catch (e) { if (e.message.includes('not found')) { /* re-list compositions and retry */ } }

When it happens

Trigger: Calling the MCP tool with an id that does not exist (typo, stale id after a composition was renamed/removed, or compositions not yet loaded).

Common situations: Renaming or deleting a composition while an MCP session holds the old id, or asking the model to select a composition before Studio finished registering compositions.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• sequenceId must be a non-empty string.
• Studio sequence selection is unavailable.
• Asset was not found in public/.
• assetPath must be a non-empty public-folder path, or an…
• Composition not found.

AI-assisted analysis of remotion-dev/remotion@46a3a6bf13 (2026-08-28). Data as JSON: /api/errors/b33a31f3a8953a07. Report an issue: GitHub.

Appendix: source

Thrown at packages/studio/src/components/WebMcp.tsx:905

					name: 'select_composition',
					title: 'Select Studio composition',
					description:
						'Open a registered composition in Remotion Studio by name.',
					inputSchema: {
						type: 'object',
						properties: {
							compositionName: {
								type: 'string',
								description: 'The name of the composition to open.',
							},
						},
						required: ['compositionName'],
						additionalProperties: false,
					},
					annotations: {readOnlyHint: false},
					execute: ({compositionName}) => {
						if (typeof compositionName !== 'string') {
							throw new Error('compositionName must be a string.');
						}

						const composition = compositionsRef.current.find(
							(candidate) => candidate.id === compositionName,
						);
						if (!composition) {
							throw new Error(`Composition ${compositionName} not found.`);
						}

						selectComposition(composition, true);
						return Promise.resolve({
							currentContent: {
								type: 'composition',
								compositionId: composition.id,
							},
						});
					},
				},

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