Get Diagnostics

curl --request POST \
  --url https://api.example.com/tools/get_diagnostics

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.example.com/tools/get_diagnostics",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.example.com/tools/get_diagnostics"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.example.com/tools/get_diagnostics")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

{
  "diagnostics": [
    {
      "range": {
        "start": {},
        "end": {}
      },
      "severity": 123,
      "code": "<string>",
      "message": "<string>",
      "source": "<string>"
    }
  ],
  "errorCount": 123,
  "warningCount": 123
}

POST

tools

get_diagnostics

Get Diagnostics

curl --request POST \
  --url https://api.example.com/tools/get_diagnostics

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.example.com/tools/get_diagnostics",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.example.com/tools/get_diagnostics"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.example.com/tools/get_diagnostics")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

{
  "diagnostics": [
    {
      "range": {
        "start": {},
        "end": {}
      },
      "severity": 123,
      "code": "<string>",
      "message": "<string>",
      "source": "<string>"
    }
  ],
  "errorCount": 123,
  "warningCount": 123
}

Overview

Get real-time diagnostics (errors, warnings, and informational messages) for your Python code. This provides the same error detection you see in your IDE’s Problems panel.

Request

string

required

File URI (e.g., file:///workspace/main.py)

string

Filter by severity: error, warning, information, hint

Response

array

Array of diagnostic messages

Show Diagnostic

object

Location of the issue

Show Range

object

Start position (line, character)

object

End position (line, character)

number

Severity level: 1 (Error), 2 (Warning), 3 (Information), 4 (Hint)

string

Error code (e.g., undefined-variable, type-mismatch)

string

Human-readable description of the issue

string

Always Pylance for this server

number

Total number of errors

number

Total number of warnings

Example Request

curl -X POST https://api.pylancemcp.dev/v1/tools/call \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "get_diagnostics",
    "arguments": {
      "uri": "file:///workspace/app/views.py"
    }
  }'

from pylance_mcp import Client

client = Client(api_key="YOUR_API_KEY")

diagnostics = client.get_diagnostics(
    uri="file:///workspace/app/views.py"
)

print(f"Errors: {diagnostics.error_count}")
print(f"Warnings: {diagnostics.warning_count}")

for diag in diagnostics.diagnostics:
    severity = ["", "ERROR", "WARNING", "INFO", "HINT"][diag.severity]
    print(f"{severity} at line {diag.range.start.line + 1}: {diag.message}")

import { PylanceMCP } from '@pylance-mcp/client';

const client = new PylanceMCP({ apiKey: 'YOUR_API_KEY' });

const diagnostics = await client.getDiagnostics({
  uri: 'file:///workspace/app/views.py'
});

console.log(`Errors: ${diagnostics.errorCount}`);
console.log(`Warnings: ${diagnostics.warningCount}`);

diagnostics.diagnostics.forEach(diag => {
  const severity = ["", "ERROR", "WARNING", "INFO", "HINT"][diag.severity];
  console.log(`${severity} at line ${diag.range.start.line + 1}: ${diag.message}`);
});

import { PylanceMCP, DiagnosticsRequest } from '@pylance-mcp/client';

const client = new PylanceMCP({ apiKey: process.env.PYLANCE_API_KEY! });

const request: DiagnosticsRequest = {
  uri: 'file:///workspace/app/views.py'
};

const diagnostics = await client.getDiagnostics(request);

console.log(`Errors: ${diagnostics.errorCount}`);
console.log(`Warnings: ${diagnostics.warningCount}`);

for (const diag of diagnostics.diagnostics) {
  const severity = ["", "ERROR", "WARNING", "INFO", "HINT"][diag.severity];
  console.log(`${severity} at line ${diag.range.start.line + 1}: ${diag.message}`);
}

Example Response

{
  "diagnostics": [
    {
      "range": {
        "start": { "line": 15, "character": 8 },
        "end": { "line": 15, "character": 21 }
      },
      "severity": 1,
      "code": "undefined-variable",
      "message": "\"undefined_var\" is not defined",
      "source": "Pylance"
    },
    {
      "range": {
        "start": { "line": 23, "character": 12 },
        "end": { "line": 23, "character": 26 }
      },
      "severity": 2,
      "code": "type-mismatch",
      "message": "Argument of type \"str\" cannot be assigned to parameter \"amount\" of type \"int\" in function \"calculate\"",
      "source": "Pylance"
    },
    {
      "range": {
        "start": { "line": 42, "character": 0 },
        "end": { "line": 42, "character": 6 }
      },
      "severity": 3,
      "code": "unused-import",
      "message": "Import \"typing\" is not accessed",
      "source": "Pylance"
    }
  ],
  "errorCount": 1,
  "warningCount": 1
}

Diagnostic Types

Errors (Severity 1)

Code	Description	Example
`undefined-variable`	Variable not defined	`print(unknown_var)`
`type-mismatch`	Type doesn’t match expected	`calculate("5")` when expecting `int`
`import-not-found`	Module cannot be imported	`import nonexistent_module`
`syntax-error`	Invalid Python syntax	`def foo(` (missing closing paren)
`missing-argument`	Required parameter not provided	`calculate()` when `calculate(x)` expected

Warnings (Severity 2)

Code	Description	Example
`unused-import`	Import never used	`import os` but `os` not referenced
`unused-variable`	Variable assigned but never used	`temp = 5` but `temp` not used
`duplicate-import`	Module imported multiple times	`import json` twice
`unreachable-code`	Code that will never execute	Code after `return`
`deprecated`	Using deprecated functionality	`collections.Mapping` instead of `collections.abc.Mapping`

Information (Severity 3)

Code	Description	Example
`missing-type-hint`	Type annotation missing	`def foo(x):` instead of `def foo(x: int):`
`convention-violation`	Style guideline not followed	Function name not snake_case

Use Cases

Pre-Commit Validation

# Check for errors before committing
files_to_check = get_changed_files()

for file in files_to_check:
    diagnostics = client.get_diagnostics(uri=file)
    
    if diagnostics.error_count > 0:
        print(f"❌ Cannot commit: {file} has errors")
        for diag in diagnostics.diagnostics:
            if diag.severity == 1:
                print(f"  Line {diag.range.start.line + 1}: {diag.message}")
        exit(1)

print("✅ All files are error-free")

Continuous Monitoring

# Watch for new errors as code changes
def monitor_file(file_uri):
    previous_errors = set()
    
    while True:
        diagnostics = client.get_diagnostics(uri=file_uri)
        current_errors = {
            (d.range.start.line, d.message) 
            for d in diagnostics.diagnostics 
            if d.severity == 1
        }
        
        # New errors appeared
        new_errors = current_errors - previous_errors
        if new_errors:
            for line, message in new_errors:
                print(f"🚨 New error at line {line + 1}: {message}")
        
        previous_errors = current_errors
        time.sleep(2)

Code Quality Metrics

# Calculate code quality score
def calculate_quality_score(workspace_files):
    total_errors = 0
    total_warnings = 0
    
    for file in workspace_files:
        diagnostics = client.get_diagnostics(uri=file)
        total_errors += diagnostics.error_count
        total_warnings += diagnostics.warning_count
    
    # Score: 100 - (10 * errors) - (2 * warnings)
    score = max(0, 100 - (10 * total_errors) - (2 * total_warnings))
    
    return {
        "score": score,
        "errors": total_errors,
        "warnings": total_warnings,
        "grade": "A" if score >= 90 else "B" if score >= 80 else "C"
    }

Filtering by Severity

Get only specific severity levels:

diagnostics = client.get_diagnostics(
    uri="file:///workspace/app/views.py",
    severity="error"
)

# Only severity 1 (errors) returned

diagnostics = client.get_diagnostics(
    uri="file:///workspace/app/views.py"
)

# Filter client-side
critical = [d for d in diagnostics.diagnostics if d.severity <= 2]

Performance Tips

Incremental Updates: Only check files that changed, not entire workspace

Debounce Checks: Wait 500ms-1s after typing stops before checking

Cache Results: Diagnostics don’t change unless file changes

Error Responses

Code	Reason	Solution
`FILE_NOT_FOUND`	File doesn’t exist	Verify file path
`INVALID_PYTHON`	File is not Python	Check file extension and content
`PARSE_ERROR`	Cannot parse file	File has syntax errors preventing analysis
`WORKSPACE_NOT_LOADED`	Workspace still loading	Wait for initialization

Rate Limits

Tier	Requests/Hour	Requests/Day
Free	20	100
Hobby	500	5,000
Pro	5,000	50,000
Enterprise	Unlimited	Unlimited

Get Code Actions

Get quick fixes for diagnostics

Format Document

Auto-format code to fix style issues

Get Hover

Get more info about errors

Apply Workspace Edit

Apply fixes automatically

Get Started

Core Concepts

Guides

API Reference

Deployment

Get Diagnostics

Overview

Request

Response

Example Request

Example Response

Diagnostic Types

Errors (Severity 1)

Warnings (Severity 2)

Information (Severity 3)

Use Cases

Pre-Commit Validation

Continuous Monitoring

Code Quality Metrics

Filtering by Severity

Performance Tips

Error Responses

Rate Limits

Get Code Actions

Format Document

Get Hover

Apply Workspace Edit

​Overview

​Request

​Response

​Example Request

​Example Response

​Diagnostic Types

​Errors (Severity 1)

​Warnings (Severity 2)

​Information (Severity 3)

​Use Cases

​Pre-Commit Validation

​Continuous Monitoring

​Code Quality Metrics

​Filtering by Severity

​Performance Tips

​Error Responses

​Rate Limits

​Related Tools

Get Code Actions

Format Document

Get Hover

Apply Workspace Edit

Overview

Request

Response

Example Request

Example Response

Diagnostic Types

Errors (Severity 1)

Warnings (Severity 2)

Information (Severity 3)

Use Cases

Pre-Commit Validation

Continuous Monitoring

Code Quality Metrics

Filtering by Severity

Performance Tips

Error Responses

Rate Limits

Related Tools