A bug report that says "the API returns 400" is unhelpful; a bug report containing the exact cURL command is actionable.
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API Request Builder
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Free · API · MCPToolYour platform
Use API Request Builder three ways
The free API Request Builder on this page works in your browser. The same workflow is available via REST API for apps and via MCP for Cursor, Claude, and other agents — one API key, one plan, one quota. This tool is part of the developer-apis module under Developer Tools.
- Free in browserUse API Request Builder here — no account required.
- REST APICall from your server with
X-Api-Key. - MCP for agentsConnect Cursor or Claude to ToolYour MCP with the same key.
- 1. Get an API keySign in and open Dashboard → API Keys (works for REST and MCP).
- 2. Call or connectUse the REST API from your server, or paste the MCP URL into your agent config.
- 3. Same qualityOutput matches the free web tool across all three surfaces.
What is API Request Builder?
A bug report that says "the API returns 400" is unhelpful; a bug report containing the exact cURL command is actionable. This API request builder takes a method, URL, header object, and optional body, then returns both a properly escaped cURL command and an equivalent JavaScript fetch call ready to paste into a ticket, a runbook, or documentation.
Quoting is the part it saves you from. Header values with spaces, JSON bodies containing double quotes, and URLs with query strings are all escaped correctly, which is where hand-written cURL examples usually break for the person trying to reproduce them. The tool composes only — it never sends the request, so there is no response, no status code, and no risk of triggering a side effect from a page. To actually observe what an endpoint returns, HTTP Headers Checker performs a real GET, and JWT Generator mints the test token for your Authorization header.
Browser use is free and needs no signup. The same job runs over REST at POST https://api.toolyour.com/api/v1/developer-apis/api-request-builder and over MCP at https://api.toolyour.com/mcp — one API key, one shared monthly credit pool, 1 credit per successful call.
What are common questions about API Request Builder?
Does it send the request?
No. It only composes snippets. Nothing leaves the server, so building a DELETE example is completely safe.
How should headers be supplied?
As a JSON object of key and value pairs, or a JSON string containing one. Values are escaped correctly in both outputs.
Are both cURL and fetch returned?
Yes, from a single call — cURL for terminals and CI, and a fetch example for browser or Node code.
What are the key features of API Request Builder?
Two snippets per call
A cURL command and a matching fetch example generated from the same inputs.
Correct escaping
Quotes in JSON bodies and spaces in header values are handled so the snippet runs as written.
Zero side effects
Nothing is transmitted, which makes it safe for destructive method examples.
How do you use API Request Builder?
Set the method and URL
Include the full query string exactly as the client sends it.
Add headers and body
Supply headers as a JSON object and paste the request body if there is one.
Copy the snippet
Paste into a ticket, a runbook, or your terminal to reproduce the call.
A reproducible request is a better bug report
The gap between "it fails for me" and a fixed bug is usually reproduction. A complete cURL command closes it: the reader runs one line and sees the same failure, with no guessing about which header was set or how the body was serialised.
Two habits make it safe to share. Redact credentials before pasting — replace the token with a placeholder and note where a valid one comes from. Include the failing case only, not your whole session, so the reader is not sifting through requests that worked. A short, precise command is far more likely to be run than a long transcript.
Building and observing requests together
This tool covers composition; two neighbours cover the rest of the loop. JWT Generator produces the HS256 test token that goes into the Authorization header, and HTTP Headers Checker performs a real GET when you need to see what the origin actually returns.
If the body is JSON, run it through JSON Formatter first. A body that does not parse produces a 400 that has nothing to do with your endpoint logic, and catching that before you build the snippet saves a round of confusion.
Which HTTP / auth helper tools sit in this cluster?
Where do you browse more developer tools tools?
- Developer Tools tools
Browse the full Developer Tools category on ToolYour.
- Marketing Tools tools
Build UTM links, check ads copy limits, QA email subjects, and calculate ROAS/CPC/CTR — free in the browser; R
- Security Tools tools
Check HTTP security headers, TLS, cookies, JWTs, passwords, hashes, and SPF/DKIM/DMARC — free in the browser;
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