Postmancer
A standalone MCP server for API testing and management — let AI assistants call REST APIs in natural language.
Add to your client
Copy the config for your MCP client and paste it into its config file.
npm install -g postmancerPaste into ~/Library/Application Support/Claude/claude_desktop_config.json
{
"mcpServers": {
"postmancer": {
"command": "npx",
"args": [
"-y",
"postmancer"
],
"env": {
"LOG_LEVEL": "info"
}
}
}
}Step-by-step guides: Add to Claude Desktop · Add to Cursor · Add to Windsurf
Before you start
- Node.js with npm/npx (to run the package), or Docker
- A REST API to test against
About Postmancer
Postmancer is a standalone MCP server that turns an AI assistant into a REST API client. It can send HTTP requests to any URL, save and organize requests into collections, substitute environment variables into request templates, and authenticate using Basic, Bearer, API Key, or OAuth2. It is positioned as an AI-assistant-focused alternative to tools like Postman and Insomnia.
Tools & capabilities (7)
http_requestSend HTTP requests to any URL.
list_collectionsView all your saved API collections.
list_requestsView all requests in a collection.
save_requestSave a request to a collection.
request_from_collectionExecute a saved request from a collection.
set_environment_variableSet variables for request templates.
get_environment_variablesView all environment variables.
When to use it
- Make ad-hoc HTTP requests to a REST API through natural language
- Build and reuse collections of saved API requests
- Manage environment variables and substitute them into request templates
- Test API endpoints with various authentication methods (Basic, Bearer, API Key, OAuth2)
Security notes
For production environments it is strongly recommended to set the encryption keys (POSTMANCER_ENCRYPTION_KEY for credentials/tokens, ENCRYPTION_KEY for secret environment variables) rather than using the defaults. If unset, a random key is generated for POSTMANCER_ENCRYPTION_KEY and a default key is used for ENCRYPTION_KEY.
Postmancer FAQ
How do I run Postmancer?
Install it globally with `npm install -g postmancer` or run it directly via `npx postmancer`. A Docker image is also available.
Where are collections stored?
By default in `~/.postmancer`. You can change this with the `COLLECTIONS_PATH` environment variable.
How are credentials kept secure?
Credentials and tokens are encrypted using `POSTMANCER_ENCRYPTION_KEY`, and secret environment variables using `ENCRYPTION_KEY`. Setting these keys explicitly is strongly recommended in production.
What authentication methods are supported?
Basic, Bearer, API Key, and OAuth2.
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