--- updatedAt: 2025-07-26T16:54:38.000Z agentTools: projectIndex: https://docs.metakeep.xyz/llms.txt --- # Read Lambda Data After the lambda is created from the `/v2/app/lambda/create` or imported using `/v2/app/lambda/import` API call, use this API to read data from the read-only or getter function(also known as the view-only function in solidity). Calling a non-read function will result in an error. JSON response `data` field contains the return value of the read-only function. The `data` field format follows specification [here](https://docs.metakeep.xyz/reference/lambda-101#solidity-types-to-lambda-types). Here are some examples: ```json Read tokenURI response // Read smart contract data: tokenURI(uint256 tokenId) { "status": "SUCCESS", "data": "https://api.dev.metakeep.xyz/v2/nft/metadata?chain=80002&collection=0x5059221e0971b1761f71a9619932c2b395c266d2&token=70247059" } ``` ```json Read ownerOf response // Read smart contract data: ownerOf(uint256 tokenId) { "status": "SUCCESS", "data": "0x6B40cA2814198A37BA5798B0C5EE1A2E029b997f" } ``` ```json Read array response // Read from a function that returns an array { "status": "SUCCESS", "data": [ "0x6B40cA2814198A37BA5798B0C5EE1A2E029b997f", "123" ] } ``` If the contract function throws an error, the response will contain the error message and the status will be `FUNCTION_FAILURE`. Here's an example ```json Contract function failure response /* This function gets balance of the user. function balanceOf(address of) public view virtual { require(to != address(0), "ERC721: balance query for the zero address"); return _balance[of]; } */ // Call balanceOf with zero address. // The response will have the error message. { "status": "FUNCTION_FAILURE", "failureReason": "ERC721: balance query for the zero address" } ``` > 👍 This API doesn't consume any gas. > > You don't need to pay any gas fee when using this API. It's okay to call this API several times without having to worry about paying for blockchain transactions. ## Data Reading Limits The API has limits on the amount of data(**gas< 200M**) that can be returned in a single call and the time it takes to execute the function call. Trying to read too much data can result in failure and cause a **poor user experience** due to higher latency. This also prevents reading from functions that can go in an infinite loop. For best results, we recommend the following: * **Only read the data you need.** If you need to read a lot of data, consider breaking it up into multiple calls. * **Use Pagination**. If you need to read all data, design your function so that instead of returning all the data, it returns a page of data. You can then use the pagination parameters to retrieve the next page of data. * **Store data in database**. Consider storing the large data in your own database instead (SQL, S3, etc). *Note that if you have already deployed the lambda contract, you can update the contract to add pagination parameters if the contract is upgradable or deploy a new contract with pagination parameters which will read the data from your existing contract.* ## Error Status > 🚧 Api Error Status > > You can find error status returned by the api [here](https://docs.metakeep.xyz/reference/api-error-status#v2applambdaread). © Copyright 2024, Passbird Research Inc. # OpenAPI definition ```json { "openapi": "3.1.0", "info": { "title": "production", "version": "3.4" }, "servers": [ { "url": "https://api.metakeep.xyz/" } ], "components": { "securitySchemes": { "sec0": { "type": "apiKey", "in": "header", "name": "x-api-key" } } }, "security": [ { "sec0": [] } ], "paths": { "/v2/app/lambda/read": { "post": { "summary": "Read Lambda Data", "description": "", "operationId": "v2applambdaread", "requestBody": { "content": { "application/json": { "schema": { "type": "object", "required": [ "lambda", "function" ], "properties": { "lambda": { "type": "string", "description": "Hex encoded lambda address. This is obtained from a previous `/v2/app/lambda/create` or `/v2/app/lambda/import` API call" }, "function": { "type": "object", "description": "Lambda Function with arguments to read the data from in the format `{ name: \"function_name\", args: [] }`. `Args` list can be left empty if the function takes no arguments.", "required": [ "name" ], "properties": { "name": { "type": "string", "description": "Function name.", "default": "function_name" }, "args": { "type": "array", "description": "Array of function arguments. This can be left empty if the function takes no arguments. Arguments should be sent in the format described [here](https://docs.metakeep.xyz/reference/lambda-101#solidity-types-to-lambda-types).", "default": [ "123" ], "items": { "type": "string" } } } } } } } } }, "responses": { "200": { "description": "200", "content": { "application/json": { "examples": { "Result": { "value": "{\n \"status\": \"SUCCESS\",\n \"data\": \"2.05\"\n}" }, "Read array": { "value": "{\n \"status\": \"SUCCESS\",\n \"data\": [\n \"2.05\",\n \"0x1234\"\n ]\n}" }, "Contract function failure": { "value": "{\n \"status\": \"FUNCTION_FAILURE\",\n \"failureReason\": \"ERC721: balance query for the zero address\"\n}" } }, "schema": { "oneOf": [ { "type": "object", "properties": { "status": { "type": "string", "example": "SUCCESS" }, "data": { "type": "string", "example": "2.05" } } }, { "title": "Read array", "type": "object", "properties": { "status": { "type": "string", "example": "SUCCESS" }, "data": { "type": "array", "items": { "type": "string", "example": "2.05" } } } }, { "title": "Contract function failure", "type": "object", "properties": { "status": { "type": "string", "example": "FUNCTION_FAILURE" }, "failureReason": { "type": "string", "example": "ERC721: balance query for the zero address" } } } ] } } } } }, "deprecated": false } } }, "x-readme": { "headers": [], "explorer-enabled": true, "proxy-enabled": true }, "x-readme-fauxas": true } ```