API recipes¶

This page collects copy-paste recipes for talking to the md-bridge HTTP API from the three places contributors and operators ask about: the shell (curl), Python (requests), and the browser or Node (fetch).

The API is documented endpoint-by-endpoint at /docs (Swagger UI on the running service). This page focuses on the practical "give me a working snippet" angle.

Endpoints at a glance¶

Method	Path	Purpose	Request body	Response
`GET`	`/api/health`	Liveness probe	empty	`{ "status": "ok" }`
`POST`	`/api/inspect-pdf`	Read PDF metadata without converting	`multipart/form-data` (file)	JSON
`POST`	`/api/pdf-to-md`	Convert PDF to Markdown	`multipart/form-data` (file + options)	JSON
`POST`	`/api/md-to-pdf`	Render Markdown to PDF	`multipart/form-data` (file + options)	`application/pdf`

Default host in every recipe is http://localhost:8000. Switch to your deployed host as needed.

Upload limit on all POST endpoints is 500 MB (MAX_UPLOAD_BYTES in apps/api/app/config.py).

Health check¶

The cheapest sanity check.

curl¶

curl -sf http://localhost:8000/api/health
# => {"status":"ok"}

Python¶

import requests

r = requests.get("http://localhost:8000/api/health", timeout=5)
r.raise_for_status()
print(r.json())  # {'status': 'ok'}

JavaScript¶

const r = await fetch("http://localhost:8000/api/health");
const data = await r.json();
console.log(data); // { status: "ok" }

Inspect a PDF (no conversion)¶

Returns the document profile that the converter would build, without running the conversion. Useful for deciding whether OCR is needed before paying the conversion cost.

Response shape¶

{
  "pages": 4,
  "body_size_pt": 11.0,
  "heading_sizes_pt": [18.0, 14.0, 12.5],
  "fonts": [
    { "name": "Helvetica-Bold", "size": 18.0, "count": 6, "sample": "Introduction" }
  ],
  "tagged": false,
  "needs_ocr": false
}

needs_ocr: true means the PDF has no extractable text on at least one page; the converter would emit a needs_ocr warning unless OCR is enabled.

curl¶

curl -X POST http://localhost:8000/api/inspect-pdf \
  -F "file=@whitepaper.pdf"

Python¶

import requests

with open("whitepaper.pdf", "rb") as fh:
    r = requests.post(
        "http://localhost:8000/api/inspect-pdf",
        files={"file": ("whitepaper.pdf", fh, "application/pdf")},
        timeout=60,
    )
r.raise_for_status()
report = r.json()
if report["needs_ocr"]:
    print("This PDF is scanned. Enable MD_BRIDGE_OCR_ENABLED on the server.")

JavaScript¶

const form = new FormData();
form.append("file", fileInput.files[0]);  // browser <input type="file">

const r = await fetch("http://localhost:8000/api/inspect-pdf", {
  method: "POST",
  body: form,
});
if (!r.ok) {
  throw new Error(`Inspect failed: ${r.status}`);
}
const report = await r.json();

PDF to Markdown¶

The most common conversion.

Options¶

The options field is a JSON string. All fields are optional.

Field	Type	Default	What it does
`page_break`	bool	`false`	Inserts `---` between pages
`with_images`	bool	`false`	Extracts images to `images/<pdf_stem>/`
`front_matter`	bool	`true`	Emits YAML front matter at the top
`lang`	string	`"pt-BR"`	Affects warning translations only

Response shape¶

{
  "md": "---\ntitle: \"Whitepaper\"\npages: 4\n---\n\n# Introduction\n\n...",
  "front_matter": {
    "title": "Whitepaper",
    "author": "Author Name",
    "date": "2026-04-12",
    "source": "whitepaper.pdf",
    "pages": 4
  },
  "warnings": [],
  "stats": { "headings": 6, "tables": 1, "bullets": 14 },
  "ocr_applied": false
}

curl¶

Bare conversion:

curl -X POST http://localhost:8000/api/pdf-to-md \
  -F "file=@whitepaper.pdf"

With options and saving the Markdown to disk:

curl -X POST http://localhost:8000/api/pdf-to-md \
  -F "file=@whitepaper.pdf" \
  -F 'options={"page_break": true, "front_matter": true, "lang": "en"}' \
  | jq -r '.md' > whitepaper.md

Python¶

import json
import requests

with open("whitepaper.pdf", "rb") as fh:
    r = requests.post(
        "http://localhost:8000/api/pdf-to-md",
        files={"file": ("whitepaper.pdf", fh, "application/pdf")},
        data={"options": json.dumps({"front_matter": True, "lang": "en"})},
        timeout=300,
    )
r.raise_for_status()
result = r.json()

if result["warnings"]:
    print("Warnings:", result["warnings"])
print(f"Extracted {result['stats']['headings']} headings, "
      f"{result['stats']['tables']} tables, "
      f"{result['stats']['bullets']} bullets")

with open("whitepaper.md", "w", encoding="utf-8") as fh:
    fh.write(result["md"])

JavaScript¶

Browser flow that posts a <input type="file"> and downloads the Markdown as a file:

const form = new FormData();
form.append("file", fileInput.files[0]);
form.append("options", JSON.stringify({ front_matter: true, lang: "en" }));

const r = await fetch("http://localhost:8000/api/pdf-to-md", {
  method: "POST",
  body: form,
});
if (!r.ok) {
  const err = await r.json().catch(() => ({}));
  throw new Error(err.error?.message ?? `HTTP ${r.status}`);
}
const data = await r.json();

const blob = new Blob([data.md], { type: "text/markdown" });
const url = URL.createObjectURL(blob);
const link = document.createElement("a");
link.href = url;
link.download = "converted.md";
link.click();
URL.revokeObjectURL(url);

Node.js with undici's FormData (Node 20+):

import { readFile } from "node:fs/promises";
import { writeFile } from "node:fs/promises";

const buf = await readFile("whitepaper.pdf");
const form = new FormData();
form.append("file", new Blob([buf], { type: "application/pdf" }), "whitepaper.pdf");
form.append("options", JSON.stringify({ lang: "en" }));

const r = await fetch("http://localhost:8000/api/pdf-to-md", { method: "POST", body: form });
const result = await r.json();
await writeFile("whitepaper.md", result.md);

Markdown to PDF¶

The renderer returns the PDF as the raw response body (application/pdf), with a Content-Disposition: attachment; filename="<name>.pdf" header.

Options¶

Field	Type	Default	What it does
`lang`	string	`"pt-BR"`	Sets `<html lang>` and affects hyphenation hints

curl¶

curl -X POST http://localhost:8000/api/md-to-pdf \
  -F "file=@notes.md" \
  --output notes.pdf

With language option:

curl -X POST http://localhost:8000/api/md-to-pdf \
  -F "file=@notes.md" \
  -F 'options={"lang": "en"}' \
  --output notes.pdf

Python¶

import json
import requests

with open("notes.md", "rb") as fh:
    r = requests.post(
        "http://localhost:8000/api/md-to-pdf",
        files={"file": ("notes.md", fh, "text/markdown")},
        data={"options": json.dumps({"lang": "en"})},
        timeout=300,
    )
r.raise_for_status()

with open("notes.pdf", "wb") as fh:
    fh.write(r.content)

JavaScript¶

Browser flow that posts a Markdown file and triggers a download of the PDF:

const form = new FormData();
form.append("file", fileInput.files[0]);
form.append("options", JSON.stringify({ lang: "en" }));

const r = await fetch("http://localhost:8000/api/md-to-pdf", {
  method: "POST",
  body: form,
});
if (!r.ok) throw new Error(`HTTP ${r.status}`);

const blob = await r.blob();
const url = URL.createObjectURL(blob);
const link = document.createElement("a");
link.href = url;
link.download = "rendered.pdf";
link.click();
URL.revokeObjectURL(url);

Error handling¶

Every failure returns the same envelope:

{
  "error": {
    "code": "<machine_readable>",
    "message": "<human_readable>",
    "detail": "<optional, varies by code>"
  }
}

The HTTP status reflects the class of error:

Status	Code examples	When
`400`	`wrong_file_type`	The upload's filename does not match the expected extension
`413`	`payload_too_large`	The upload exceeded 500 MB
`422`	`invalid_options`	The `options` JSON failed to parse or failed Pydantic validation
`500`	depends	Renderer crashed, OS dep missing, etc.

Reading the envelope¶

curl¶

curl -sf -X POST http://localhost:8000/api/md-to-pdf \
  -F "file=@notes.txt" \
  --output notes.pdf

echo $?   # non-zero on failure; --fail-with-body prints the JSON

Pretty-printing the error body:

curl -X POST http://localhost:8000/api/md-to-pdf \
  -F "file=@notes.txt" \
  --fail-with-body \
  --output - | jq .error

Python¶

import requests

r = requests.post(
    "http://localhost:8000/api/md-to-pdf",
    files={"file": ("notes.txt", b"# wrong extension", "text/plain")},
)
if not r.ok:
    err = r.json().get("error", {})
    raise RuntimeError(f"[{err.get('code')}] {err.get('message')}")

JavaScript¶

const r = await fetch("http://localhost:8000/api/md-to-pdf", {
  method: "POST",
  body: form,
});
if (!r.ok) {
  const body = await r.json().catch(() => ({}));
  const err = body.error ?? {};
  throw new Error(`[${err.code ?? r.status}] ${err.message ?? "request failed"}`);
}

CORS and cross-origin requests¶

The dev server in apps/api/app/main.py allows requests from http://localhost:5173 (the Vite dev server). For other origins, set the MD_BRIDGE_CORS_ORIGINS environment variable to a comma-separated list when starting the API:

MD_BRIDGE_CORS_ORIGINS="https://app.example.com,https://docs.example.com" \
  uvicorn app.main:app --app-dir apps/api

If the browser console shows CORS policy: No 'Access-Control-Allow-Origin', the origin making the call is not in that list.

Rate limits and concurrency¶

There is no built-in rate limiter. The conversion endpoints run the work in a thread pool via asyncio.to_thread, so concurrent requests do not block each other at the FastAPI layer, but they do share the host's CPU. Two practical knobs:

Process-level concurrency: uvicorn --workers N runs N separate Python processes. Each process serves requests in parallel.
Per-process thread cap: the default thread-pool size is min(32, os.cpu_count() + 4). PDF conversions are CPU-bound, so raising this past the core count rarely helps.

If you need a real rate limit (per-IP, per-API-key), put a reverse proxy in front (nginx with limit_req, Traefik with the rate-limit middleware, or Caddy with rate_limit).