Return CSV instead of JSON for token efficiency

.github/workflows/ci.yml

@@ -28,8 +28,8 @@ jobs:
       - name: Install dependencies
         run: uv sync
 
-      - name: Run Ruff check
-        run: uv run ruff check
+      - name: Run linter
+        run: uv run just lint
 
-      - name: Run Ruff format
-        run: uv run ruff format --check
+      - name: Run tests
+        run: uv run just test

README.md

@@ -52,7 +52,7 @@ path to `uvx`.
 
 ```bash
 # Claude CLI
-claude mcp add polygon -e POLYGON_API_KEY=your_api_key_here -- uvx --from git+https://github.com/polygon-io/mcp_polygon@v0.4.1 mcp_polygon
+claude mcp add polygon -e POLYGON_API_KEY=your_api_key_here -- uvx --from git+https://github.com/polygon-io/mcp_polygon@v0.5.0 mcp_polygon
 ```
 
 This command will install the MCP server in your current project.
@@ -83,7 +83,7 @@ Make sure you complete the various fields.
             "command": "<path_to_your_uvx_install>/uvx",
             "args": [
                 "--from",
-                "git+https://github.com/polygon-io/mcp_polygon@v0.4.1",
+                "git+https://github.com/polygon-io/mcp_polygon@v0.5.0",
                 "mcp_polygon"
             ],
             "env": {

justfile

@@ -1,3 +1,6 @@
 lint:
     uv run ruff format
     uv run ruff check --fix
+
+test:
+    uv run pytest -v tests

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": "0.2",
   "name": "mcp_polygon",
-  "version": "0.4.1",
+  "version": "0.5.0",
   "description": "MCP server providing access to Polygon.io financial market data API",
   "author": {
     "name": "Polygon.io",

pyproject.toml

@@ -1,12 +1,12 @@
 [project]
 name = "mcp_polygon"
-version = "0.4.1"
+version = "0.5.0"
 description = "A MCP server project"
 readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
-    "mcp[cli]>=1.9.3",
- "polygon-api-client>=1.15.3",
+    "mcp[cli]>=1.15.0",
+ "polygon-api-client>=1.15.4",
 ]
 [[project.authors]]
 name = "Polygon"
@@ -18,7 +18,9 @@ build-backend = "hatchling.build"
 
 [dependency-groups]
 dev = [
-    "ruff>=0.12.4",
+    "ruff>=0.13.2",
+    "pytest>=8.4.0",
+    "rust-just>=1.42.4",
 ]
 
 [project.scripts]

src/mcp_polygon/formatters.py

@@ -0,0 +1,81 @@
+import json
+import csv
+import io
+from typing import Any
+
+
+def json_to_csv(json_input: str | dict) -> str:
+    """
+    Convert JSON to flattened CSV format.
+
+    Args:
+        json_input: JSON string or dict. If the JSON has a 'results' key containing
+                   a list, it will be extracted. Otherwise, the entire structure
+                   will be wrapped in a list for processing.
+
+    Returns:
+        CSV string with headers and flattened rows
+    """
+    # Parse JSON if it's a string
+    if isinstance(json_input, str):
+        data = json.loads(json_input)
+    else:
+        data = json_input
+
+    if isinstance(data, dict) and "results" in data:
+        records = data["results"]
+    elif isinstance(data, list):
+        records = data
+    else:
+        records = [data]
+
+    flattened_records = [_flatten_dict(record) for record in records]
+
+    if not flattened_records:
+        return ""
+
+    # Get all unique keys across all records (for consistent column ordering)
+    all_keys = []
+    seen = set()
+    for record in flattened_records:
+        for key in record.keys():
+            if key not in seen:
+                all_keys.append(key)
+                seen.add(key)
+
+    output = io.StringIO()
+    writer = csv.DictWriter(output, fieldnames=all_keys, lineterminator="\n")
+    writer.writeheader()
+    writer.writerows(flattened_records)
+
+    return output.getvalue()
+
+
+def _flatten_dict(
+    d: dict[str, Any], parent_key: str = "", sep: str = "_"
+) -> dict[str, Any]:
+    """
+    Flatten a nested dictionary by joining keys with separator.
+
+    Args:
+        d: Dictionary to flatten
+        parent_key: Key from parent level (for recursion)
+        sep: Separator to use between nested keys
+
+    Returns:
+        Flattened dictionary with no nested structures
+    """
+    items = []
+    for k, v in d.items():
+        new_key = f"{parent_key}{sep}{k}" if parent_key else k
+
+        if isinstance(v, dict):
+            # Recursively flatten nested dicts
+            items.extend(_flatten_dict(v, new_key, sep=sep).items())
+        elif isinstance(v, list):
+            # Convert lists to comma-separated strings
+            items.append((new_key, str(v)))
+        else:
+            items.append((new_key, v))
+
+    return dict(items)