Free APIs & MCP Servers — One Directory
10,161 records: 4,352 free APIs and 5,809 MCP servers. Filter by type, category and authentication, save favorites and copy Base URLs — no account, no API key.
Well-documented records
A sample of records that clear the content bar. Ordering is by documentation completeness, not popularity — see the methodology.
- Account API This API is used for the classic integration. If you are just starting your implementation, refer to our new integration guide instead. The Account API provides endpoints for managing account-related entities on your platform. These related entities include account holders, accounts, bank accounts, shareholders, and verification-related documents. The management operations include actions such as creation, retrieval, updating, and deletion of them. For more information, refer to our documentation. ## Authentication Your Adyen contact will provide your API credential and an API key. To connect to the API, add an X-API-Key header with the API key as the value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YOURAPIKEY" \ ... Alternatively, you can use the username and…
- Accounting API Welcome to the Accounting API. You can use this API to access all Accounting API endpoints. ## Base URL The base URL for all API requests is https://unify.apideck.com We also provide a Mock API that can be used for testing purposes: https://mock-api.apideck.com ## Headers Custom headers that are expected as part of the request. Note that RFC7230 states header names are case insensitive. | Name | Type | Required | Description | | --------------------- | ------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- | | x-apideck-consumer-id | String | Yes | The id of the customer stored inside Apideck Vault. This can be a user id, account id, device id or whatever entity tha…
- Adyen Balance Control API The Balance Control API lets you transfer funds between merchant accounts that belong to the same legal entity and are under the same company account. ## Authentication To connect to the Balance Control API, you must authenticate your requests with an API key or basic auth username and password. To learn how you can generate these, see API credentials.Here is an example of authenticating a request with an API key: curl -H "X-API-Key: YourAPIkey" \ -H "Content-Type: application/json" \ ... Note that when going live, you need to generate API credentials to access the live endpoints. ## Versioning The Balance Control API supports versioning using a version suffix in the endpoint URL. This suffix has the following format: "vXX", where XX is the version number. For example: https://pal-test.ad…
- Adyen BinLookup API The BIN Lookup API provides endpoints for retrieving information, such as cost estimates, and 3D Secure supported version based on a given BIN. ## Authentication You need an API credential to authenticate to the API. If using an API key, add an X-API-Key header with the API key as the value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YOURAPIKEY" \ ... Alternatively, you can use the username and password to connect to the API using basic authentication, for example: curl -U "ws@Company.YOURCOMPANYACCOUNT":"YOURBASICAUTHENTICATIONPASSWORD" \ -H "Content-Type: application/json" \ ... ## Versioning The BinLookup API supports versioning using a version suffix in the endpoint URL. This suffix has the following format: "vXX", where XX is the version number. For exampl…
- Adyen Checkout API Adyen Checkout API provides a simple and flexible way to initiate and authorise online payments. You can use the same integration for payments made with cards (including 3D Secure), mobile wallets, and local payment methods (for example, iDEAL and Sofort). This API reference provides information on available endpoints and how to interact with them. To learn more about the API, visit online payments documentation. ## Authentication Each request to Checkout API must be signed with an API key. For this, get your API key from your Customer Area, and set this key to the X-API-Key header value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YOURAPIKEY" \ ... ## Versioning Checkout API supports versioning using a version suffix in the endpoint URL. This suffix has the fol…
- Adyen Data Protection API Adyen Data Protection API provides a way for you to process Subject Erasure Requests as mandated in GDPR. Use our API to submit a request to delete shopper's data, including payment details and other related information (for example, delivery address or shopper email).## Authentication Each request to the Data Protection API must be signed with an API key. Get your API Key from your Customer Area, as described in How to get the API key. Then set this key to the X-API-Key header value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YourAPIkey" \ ... Note that when going live, you need to generate a new API Key to access the live endpoints. ## Versioning Data Protection Service API supports versioning using a version suffix in the endpoint URL. This suffix has the fo…
- Adyen Payment API A set of API endpoints that allow you to initiate, settle, and modify payments on the Adyen payments platform. You can use the API to accept card payments (including One-Click and 3D Secure), bank transfers, ewallets, and many other payment methods. To learn more about the API, visit Classic integration. ## Authentication You need an API credential to authenticate to the API. If using an API key, add an X-API-Key header with the API key as the value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YOURAPIKEY" \ ... Alternatively, you can use the username and password to connect to the API using basic authentication, for example: curl -U "ws@Company.YOURCOMPANYACCOUNT":"YOURBASICAUTHENTICATIONPASSWORD" \ -H "Content-Type: application/json" \ ... ## Versioning Payment…
- Adyen Payout API A set of API endpoints that allow you to store payout details, confirm, or decline a payout. For more information, refer to Online payouts. ## Authentication To use the Payout API, you need to have two API credentials: one for storing payout details and submitting payouts, and another one for confirming or declining payouts. If you don't have the required API credentials, contact our Support Team. Both of these API credentials must be authenticated with basic authentication.The following example shows how to authenticate your request when submitting a payout: curl -U "storePayout@Company.YOURCOMPANYACCOUNT":"YOURBASICAUTHENTICATIONPASSWORD" \ -H "Content-Type: application/json" \ ... ## Versioning Payments API supports versioning using a version suffix in the endpoint URL. This suffix has…
- Adyen Recurring API The Recurring APIs allow you to manage and remove your tokens or saved payment details. Tokens should be created with validation during a payment request. For more information, refer to our Tokenization documentation. ## Authentication You need an API credential to authenticate to the API. If using an API key, add an X-API-Key header with the API key as the value, for example: curl -H "Content-Type: application/json" \ -H "X-API-Key: YOURAPIKEY" \ ... Alternatively, you can use the username and password to connect to the API using basic authentication, for example: curl -U "ws@Company.YOURCOMPANYACCOUNT":"YOURBASICAUTHENTICATIONPASSWORD" \ -H "Content-Type: application/json" \ ... ## Versioning Recurring API supports versioning using a version suffix in the endpoint URL. This suffix has t…
- Airbyte Configuration API Airbyte Configuration API https://airbyte.io. This API is a collection of HTTP RPC-style methods. While it is not a REST API, those familiar with REST should find the conventions of this API recognizable. Here are some conventions that this API follows: All endpoints are http POST methods. All endpoints accept data via application/json request bodies. The API does not accept any data via query params. The naming convention for endpoints is: localhost:8000/{VERSION}/{METHODFAMILY}/{METHODNAME} e.g. localhost:8000/v1/connections/create. For all update methods, the whole object must be passed in, even the fields that did not change. Authentication (OSS): When authenticating to the Configuration API, you must use Basic Authentication by setting the Authentication Header to Basic and base64 en…
- Apacta API for a tool to craftsmen used to register working hours, material usage and quality assurance. # Endpoint The endpoint https://app.apacta.com/api/v1 should be used to communicate with the API. API access is only allowed with SSL encrypted connection (https). # Authentication URL query authentication with an API key is used, so appending ?apikey={apikey} to the URL where {apikey} is found within Apacta settings is used for authentication # Pagination If the endpoint returns a pagination object it means the endpoint supports pagination - currently it's only possible to change pages with ?page={pagenumber} but implementing custom page sizes are on the road map. # Search/filter Is experimental but implemented in some cases - see the individual endpoints' docs for further explanation. # Ord…
- Apicurio Registry API [v2] Apicurio Registry is a datastore for standard event schemas and API designs. Apicurio Registry enables developers to manage and share the structure of their data using a REST interface. For example, client applications can dynamically push or pull the latest updates to or from the registry without needing to redeploy. Apicurio Registry also enables developers to create rules that govern how registry content can evolve over time. For example, this includes rules for content validation and version compatibility. The Apicurio Registry REST API enables client applications to manage the artifacts in the registry. This API provides create, read, update, and delete operations for schema and API artifacts, rules, versions, and metadata. The supported artifact types include: - Apache Avro schema -…
What is API Atlas?
API Atlas is a free, public directory of APIs and MCP servers. It indexes 10,161 records — 4,352 free APIs and 5,809 MCP servers across 53 topics, collected automatically from public sources (apis.guru, public-apis and the official MCP server registry). You can browse, search and filter the catalogue without an account and without an API key — and every record links to the provider's own documentation.
Records are compiled automatically and normalised, not curated by hand: descriptions are sanitised rather than rewritten, and the 53 topics are a consolidation of the source registries' overlapping category strings. The methodology documents the whole pipeline, including what is deliberately excluded.
What is an MCP server?
An MCP server (Model Context Protocol server) lets AI applications such as Claude or ChatGPT connect to external tools and data sources through a standard protocol. The directory tracks 5,809 MCP servers with their categories and authentication requirements, so you can find one that matches your stack before reading its full documentation. Start with all MCP servers or the working shortlist.
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