mcp-after-effects

Instructions

Implementation Reference

• src/index.ts:489-524 (registration)

  MCP tool registration for 'setLayerKeyframe', including description, input schema (layer/comp indices, property name, time, value), and handler that queues the command via writeCommandFile.

  server.tool(
    "setLayerKeyframe", // Corresponds to the function name in ExtendScript
    "Set a keyframe for a specific layer property at a given time.",
    {
      ...LayerIdentifierSchema, // Reuse common identifiers
      propertyName: z.string().describe("Name of the property to keyframe (e.g., 'Position', 'Scale', 'Rotation', 'Opacity')."),
      timeInSeconds: z.number().describe("The time (in seconds) for the keyframe."),
      value: KeyframeValueSchema
    },
    async (parameters) => {
      try {
        // Queue the command for After Effects
        writeCommandFile("setLayerKeyframe", parameters);
        
        return {
          content: [
            {
              type: "text",
              text: `Command to set keyframe for "${parameters.propertyName}" on layer ${parameters.layerIndex} in comp ${parameters.compIndex} has been queued.\n` +
                    `Use the "get-results" tool after a few seconds to check for confirmation.`
            }
          ]
        };
      } catch (error) {
        return {
          content: [
            {
              type: "text",
              text: `Error queuing setLayerKeyframe command: ${String(error)}`
            }
          ],
          isError: true
        };
      }
    }
  );

• src/index.ts:498-523 (handler)

  The handler function for the setLayerKeyframe tool. It writes the command and parameters to a temporary file ('ae_command.json') for the After Effects MCP Bridge Auto panel to detect and execute the corresponding ExtendScript.

  async (parameters) => {
    try {
      // Queue the command for After Effects
      writeCommandFile("setLayerKeyframe", parameters);
      
      return {
        content: [
          {
            type: "text",
            text: `Command to set keyframe for "${parameters.propertyName}" on layer ${parameters.layerIndex} in comp ${parameters.compIndex} has been queued.\n` +
                  `Use the "get-results" tool after a few seconds to check for confirmation.`
          }
        ]
      };
    } catch (error) {
      return {
        content: [
          {
            type: "text",
            text: `Error queuing setLayerKeyframe command: ${String(error)}`
          }
        ],
        isError: true
      };
    }
  }

• src/index.ts:479-482 (schema)

  Shared Zod schema for identifying target composition and layer by 1-based indices, reused in setLayerKeyframe and other layer tools.

  const LayerIdentifierSchema = {
    compIndex: z.number().int().positive().describe("1-based index of the target composition in the project panel."),
    layerIndex: z.number().int().positive().describe("1-based index of the target layer within the composition.")
  };

• src/index.ts:486-486 (schema)

  Zod schema for the keyframe value input, using z.any() for flexibility across different property types.

  const KeyframeValueSchema = z.any().describe("The value for the keyframe (e.g., [x,y] for Position, [w,h] for Scale, angle for Rotation, percentage for Opacity)");

• src/index.ts:156-170 (helper)

  Core helper function used by all command-queuing tools, including setLayerKeyframe, to write the command name and parameters to ae_command.json in TEMP dir for polling by After Effects bridge.

  function writeCommandFile(command: string, args: Record<string, any> = {}): void {
    try {
      const commandFile = path.join(process.env.TEMP || process.env.TMP || '', 'ae_command.json');
      const commandData = {
        command,
        args,
        timestamp: new Date().toISOString(),
        status: "pending"  // pending, running, completed, error
      };
      fs.writeFileSync(commandFile, JSON.stringify(commandData, null, 2));
      console.error(`Command "${command}" written to ${commandFile}`);
    } catch (error) {
      console.error("Error writing command file:", error);
    }
  }