Offering an MCP tool from APIs.io: get_playground_apis. It returns a curated set of APIs that need no key (or only an instant free one), cost nothing, and have no real-world side effects. Every entry includes an example request URL that answered HTTP 200 to an unauthenticated GET on the date shown, so it can be called with no setup. Good for testing a tool-use loop or learning what an API call looks like.
Condition: live, read-only.
How you get it: add the remote MCP server https://apis.io/mcp to Claude, Cursor, VS Code or any MCP client. No key, no sign-up and no card for this tool; the free tier works anonymously. Setup notes: https://apis.io/developer/mcp-server