Compiler API
One endpoint, six output formats. Send U source, get back C code, WebAssembly, AST, tokens, or just lint results.
Base URL: https://compiler.ulanguage.org
Machine-readable specs: OpenAPI 3.1 · MCP tools
POST /compile
POST/compile
Compile U source code. The format query parameter controls what comes back.
Query parameters
| Param | Values | Default | Description |
|---|
format | c wasm wat ast lint tokens | c | Output format |
source_type | u python | u | Input language (Python transpiles to U server-side) |
optimize | 0 1 2 3 | 2 | Optimization level (WASM only) |
Request body
Send raw source as text/plain, or wrap in JSON: {"source": "..."}.
Examples
Compile to C
# Returns JSON with generated C code
curl -X POST https://compiler.ulanguage.org/compile \
-H "Content-Type: text/plain" \
-d 'f main() -> I
r => 42'
{"ok": true, "errors": [], "warnings": [], "c": "/* Generated by u2c ... */\n#include \"u_runtime.h\"..."}
Compile to WebAssembly
# Returns raw .wasm binary (application/wasm)
curl -X POST https://compiler.ulanguage.org/compile?format=wasm \
-H "Content-Type: text/plain" \
-d 'f main() -> I
r => 42' -o output.wasm
Lint only
# Check for errors without generating code
curl -X POST https://compiler.ulanguage.org/compile?format=lint \
-H "Content-Type: text/plain" \
-d 'f main() -> I
r => 42'
{"ok": true, "errors": [], "warnings": []}
Get AST
# Returns the parsed abstract syntax tree
curl -X POST https://compiler.ulanguage.org/compile?format=ast \
-H "Content-Type: text/plain" \
-d 'f main() -> I
r => 42'
Get token stream
# Returns tokenized source
curl -X POST https://compiler.ulanguage.org/compile?format=tokens \
-H "Content-Type: text/plain" \
-d 'f main() -> I
r => 42'
Transpile Python to U, then compile
# Server-side Python → U transpilation + compile
curl -X POST 'https://compiler.ulanguage.org/compile?source_type=python' \
-H "Content-Type: text/plain" \
-d 'def fib(n):
if n <= 1: return n
return fib(n-1) + fib(n-2)'
JSON body
curl -X POST https://compiler.ulanguage.org/compile \
-H "Content-Type: application/json" \
-d '{"source": "f main() -> I\n\tr => 42"}'
GET /health
GET/health
Returns service status and available capabilities.
curl https://compiler.ulanguage.org/health
{"status": "ok", "compiler": "python-u2c", "capabilities": {"formats": ["c","wasm","wat","ast","lint","tokens"], "gcc": true, "wasi_sdk": true}}
MCP Integration
The compiler exposes MCP tool definitions at /mcp.json. AI assistants can compile, lint, and transpile U code by calling these tools.
curl https://compiler.ulanguage.org/mcp.json
Available tools: compile, compile_wasm, lint, transpile_python, ast, tokens.
Error format
Errors include source context with line numbers and column markers:
{"ok": false, "errors": ["input.u:2: error: 'xx' is not defined\n r => xx\n ^~~~"], "warnings": []}