get-block-children

Retrieve child blocks from a Notion block to access nested content and structure within your workspace.

Input Schema

TableJSON Schema

Name	Required	Description
`block_id`	Yes	The ID of the block to get children from
`page_size`	No	Number of results to return (max 100)
`start_cursor`	No	Pagination cursor

Implementation Reference

src/lib/mcp-server.ts:457-486 (handler)

The MCP tool handler for 'get-block-children' that calls NotionService.retrieveBlockChildren and handles response/error formatting.

async ({ block_id, page_size, start_cursor }) => {
  try {
    const blocks = await this.notionService.retrieveBlockChildren({
      block_id,
      page_size,
      start_cursor,
    });
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(blocks, null, 2),
        },
      ],
    };
  } catch (error) {
    console.error("Error in get-block-children tool:", error);
    return {
      content: [
        {
          type: "text",
          text: `Error: Failed to retrieve block children - ${
            (error as Error).message
          }`,
        },
      ],
      isError: true,
    };
  }
}

src/lib/mcp-server.ts:445-456 (schema)

Zod input schema for the 'get-block-children' tool parameters.

{
  block_id: z
    .string()
    .describe("The ID of the block to get children from"),
  page_size: z
    .number()
    .min(1)
    .max(100)
    .optional()
    .describe("Number of results to return (max 100)"),
  start_cursor: z.string().optional().describe("Pagination cursor"),
},

src/lib/mcp-server.ts:443-487 (registration)

Registration of the 'get-block-children' tool on the MCP server within registerBlockTools().

this.server.tool(
  "get-block-children",
  {
    block_id: z
      .string()
      .describe("The ID of the block to get children from"),
    page_size: z
      .number()
      .min(1)
      .max(100)
      .optional()
      .describe("Number of results to return (max 100)"),
    start_cursor: z.string().optional().describe("Pagination cursor"),
  },
  async ({ block_id, page_size, start_cursor }) => {
    try {
      const blocks = await this.notionService.retrieveBlockChildren({
        block_id,
        page_size,
        start_cursor,
      });
      return {
        content: [
          {
            type: "text",
            text: JSON.stringify(blocks, null, 2),
          },
        ],
      };
    } catch (error) {
      console.error("Error in get-block-children tool:", error);
      return {
        content: [
          {
            type: "text",
            text: `Error: Failed to retrieve block children - ${
              (error as Error).message
            }`,
          },
        ],
        isError: true,
      };
    }
  }
);

src/lib/notion.ts:239-249 (helper)

Supporting method in NotionService that wraps the Notion Client API call for retrieving block children.

async retrieveBlockChildren(params: BlockChildrenQuery) {
  try {
    return await this.client.blocks.children.list({
      block_id: params.block_id,
      start_cursor: params.start_cursor,
      page_size: params.page_size,
    });
  } catch (error) {
    this.handleError(error);
  }
}

Notion MCP Server