diff --git a/README.md b/README.md
index e16c212..08f87fc 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,7 @@ Reference implementations provided in this repository demonstrate common use-cas
 - [**Get User Info Server**](servers/get-user-info) - Access and return enriched user profile information from authentication providers or internal systems.
 - [**SQL Chat Server**](servers/sql) - Connect to SQL databases and automatically generate, execute, and optimize queries based on your database schema and natural language input. Enables chat-based data exploration, leveraging external Retrieval-Augmented Generation (RAG) for advanced query assistance.
 - [**External RAG Tool Server**](servers/external-rag) - Connect and execute your own Retrieval-Augmented Generation (RAG) pipelines as callable API tools. Easily integrate custom or third-party RAG flows, providing structured access and modular composition for knowledge-intensive applications.
+- [**Bilig WorkPaper Formula Readback Server**](servers/bilig-workpaper) - Write spreadsheet model inputs, recalculate formulas, and return verified before/after readback proof without Excel or browser automation.
 
 (More examples and reference implementations will be actively developed and continually updated.)
 
diff --git a/compose.yaml b/compose.yaml
index 0d106e9..d0b5421 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -16,6 +16,13 @@ services:
       context: ./servers/time
     ports:
       - 8083:8000
+  bilig-workpaper-server:
+    build:
+      context: ./servers/bilig-workpaper
+    ports:
+      - 8084:8000
+    environment:
+      BILIG_BASE_URL: ${BILIG_BASE_URL:-https://bilig.proompteng.ai}
 
 volumes:
   memory:
diff --git a/servers/bilig-workpaper/Dockerfile b/servers/bilig-workpaper/Dockerfile
new file mode 100644
index 0000000..18ed63f
--- /dev/null
+++ b/servers/bilig-workpaper/Dockerfile
@@ -0,0 +1,12 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY main.py .
+
+EXPOSE 8000
+
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]
diff --git a/servers/bilig-workpaper/README.md b/servers/bilig-workpaper/README.md
new file mode 100644
index 0000000..2e1ce5f
--- /dev/null
+++ b/servers/bilig-workpaper/README.md
@@ -0,0 +1,85 @@
+# Bilig WorkPaper OpenAPI Tool Server
+
+A FastAPI tool server for spreadsheet-backed formula calculations through Bilig WorkPaper.
+
+Use it when an agent or OpenAPI-compatible client needs to write one workbook input, recalculate formulas, and verify computed readback without opening Excel, Google Sheets, or a browser.
+
+## Quickstart
+
+```bash
+git clone https://github.com/open-webui/openapi-servers
+cd openapi-servers/servers/bilig-workpaper
+
+pip install -r requirements.txt
+uvicorn main:app --host 0.0.0.0 --reload
+```
+
+Open the docs:
+
+```text
+http://localhost:8000/docs
+```
+
+## Docker
+
+```bash
+docker compose up
+```
+
+## Configuration
+
+By default, this server calls the hosted Bilig demo:
+
+```text
+https://bilig.proompteng.ai
+```
+
+Set `BILIG_BASE_URL` to point at a self-hosted Bilig app:
+
+```bash
+export BILIG_BASE_URL=http://localhost:4321
+```
+
+## Endpoint
+
+```text
+POST /forecast/readback
+```
+
+Request:
+
+```json
+{
+  "sheetName": "Inputs",
+  "address": "B3",
+  "value": 0.4
+}
+```
+
+Response:
+
+```json
+{
+  "verified": true,
+  "editedCell": "Inputs!B3",
+  "before": {
+    "expectedArr": 60000,
+    "targetGap": -34000
+  },
+  "after": {
+    "expectedArr": 96000,
+    "targetGap": 5600
+  },
+  "checks": {
+    "formulasPersisted": true,
+    "restoredMatchesAfter": true,
+    "computedOutputChanged": true
+  },
+  "source": "Bilig WorkPaper",
+  "github": "https://github.com/proompteng/bilig"
+}
+```
+
+## Why This Exists
+
+Spreadsheet logic often drives pricing, forecasts, approvals, and payout rules. UI automation can click the wrong cell, and cached XLSX values can be stale. This server gives OpenAPI-compatible agents a narrow, typed API that returns proof that formulas recalculated after the edit.
diff --git a/servers/bilig-workpaper/compose.yaml b/servers/bilig-workpaper/compose.yaml
new file mode 100644
index 0000000..595e206
--- /dev/null
+++ b/servers/bilig-workpaper/compose.yaml
@@ -0,0 +1,7 @@
+services:
+  bilig-workpaper-server:
+    build: .
+    ports:
+      - "8084:8000"
+    environment:
+      BILIG_BASE_URL: ${BILIG_BASE_URL:-https://bilig.proompteng.ai}
diff --git a/servers/bilig-workpaper/main.py b/servers/bilig-workpaper/main.py
new file mode 100644
index 0000000..cdee0e8
--- /dev/null
+++ b/servers/bilig-workpaper/main.py
@@ -0,0 +1,162 @@
+import os
+from typing import Any
+
+import requests
+from fastapi import FastAPI, HTTPException
+from fastapi.middleware.cors import CORSMiddleware
+from pydantic import BaseModel, Field
+
+
+DEFAULT_BILIG_BASE_URL = "https://bilig.proompteng.ai"
+
+app = FastAPI(
+    title="Bilig WorkPaper Formula Readback API",
+    version="0.1.0",
+    description=(
+        "OpenAPI tool server for writing one Bilig WorkPaper input cell, "
+        "recalculating formulas, and returning verified computed readback."
+    ),
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+class FormulaReadbackRequest(BaseModel):
+    sheetName: str = Field(
+        "Inputs",
+        description="Worksheet containing the editable forecast input.",
+        examples=["Inputs"],
+    )
+    address: str = Field(
+        "B3",
+        description="A1-style input cell address to edit before recalculation.",
+        examples=["B3"],
+    )
+    value: float = Field(
+        0.4,
+        description="Numeric value to write before formula readback.",
+        examples=[0.4],
+    )
+
+
+class FormulaSnapshot(BaseModel):
+    expectedArr: float | None = Field(None, description="Computed expected ARR value.")
+    targetGap: float | None = Field(None, description="Computed gap to target value.")
+
+
+class FormulaChecks(BaseModel):
+    formulasPersisted: bool = Field(
+        ..., description="Formula definitions persisted after serialization."
+    )
+    restoredMatchesAfter: bool = Field(
+        ..., description="Restored workbook readback matched post-edit values."
+    )
+    computedOutputChanged: bool = Field(
+        ..., description="Dependent formula output changed after the input edit."
+    )
+
+
+class FormulaReadbackResponse(BaseModel):
+    verified: bool = Field(
+        ..., description="True only when Bilig verified the formula readback proof."
+    )
+    editedCell: str | None = Field(
+        None, description="Edited worksheet cell, for example Inputs!B3."
+    )
+    before: FormulaSnapshot
+    after: FormulaSnapshot
+    checks: FormulaChecks
+    source: str = Field("Bilig WorkPaper", description="Readback source.")
+    github: str = Field(
+        "https://github.com/proompteng/bilig", description="Bilig project URL."
+    )
+
+
+def bilig_base_url() -> str:
+    base_url = os.getenv("BILIG_BASE_URL", DEFAULT_BILIG_BASE_URL).rstrip("/")
+    if not base_url.startswith(("http://", "https://")):
+        raise HTTPException(
+            status_code=500, detail="BILIG_BASE_URL must start with http:// or https://"
+        )
+    return base_url
+
+
+def compact_proof(proof: dict[str, Any]) -> FormulaReadbackResponse:
+    if proof.get("verified") is not True:
+        raise HTTPException(
+            status_code=502,
+            detail={"message": "Bilig returned an unverified response", "proof": proof},
+        )
+
+    before = proof.get("before") if isinstance(proof.get("before"), dict) else {}
+    after = proof.get("after") if isinstance(proof.get("after"), dict) else {}
+    checks = proof.get("checks") if isinstance(proof.get("checks"), dict) else {}
+
+    return FormulaReadbackResponse(
+        verified=True,
+        editedCell=proof.get("editedCell"),
+        before=FormulaSnapshot(
+            expectedArr=before.get("expectedArr"),
+            targetGap=before.get("targetGap"),
+        ),
+        after=FormulaSnapshot(
+            expectedArr=after.get("expectedArr"),
+            targetGap=after.get("targetGap"),
+        ),
+        checks=FormulaChecks(
+            formulasPersisted=checks.get("formulasPersisted") is True,
+            restoredMatchesAfter=checks.get("restoredMatchesAfter") is True,
+            computedOutputChanged=checks.get("computedOutputChanged") is True,
+        ),
+    )
+
+
+@app.get("/health", summary="Health check")
+def health() -> dict[str, str]:
+    return {"status": "ok"}
+
+
+@app.post(
+    "/forecast/readback",
+    response_model=FormulaReadbackResponse,
+    summary="Write one forecast input and return verified formula readback",
+)
+def forecast_readback(request: FormulaReadbackRequest) -> FormulaReadbackResponse:
+    try:
+        response = requests.post(
+            f"{bilig_base_url()}/api/workpaper/n8n/forecast",
+            json={
+                "sheetName": request.sheetName,
+                "address": request.address.upper(),
+                "value": request.value,
+            },
+            headers={
+                "Accept": "application/json",
+                "User-Agent": "OpenWebUI-Bilig-WorkPaper-Server/0.1",
+            },
+            timeout=30,
+        )
+        response.raise_for_status()
+        proof = response.json()
+    except requests.exceptions.RequestException as error:
+        raise HTTPException(
+            status_code=503, detail=f"Error connecting to Bilig: {error}"
+        ) from error
+    except ValueError as error:
+        raise HTTPException(
+            status_code=502, detail=f"Bilig returned invalid JSON: {error}"
+        ) from error
+
+    if not isinstance(proof, dict):
+        raise HTTPException(
+            status_code=502,
+            detail=f"Expected JSON object from Bilig, received {type(proof).__name__}",
+        )
+
+    return compact_proof(proof)
diff --git a/servers/bilig-workpaper/requirements.txt b/servers/bilig-workpaper/requirements.txt
new file mode 100644
index 0000000..e1de28b
--- /dev/null
+++ b/servers/bilig-workpaper/requirements.txt
@@ -0,0 +1,4 @@
+fastapi
+uvicorn[standard]
+pydantic
+requests