Universal MCP Client

Connect to any MCP server without bloating context with tool definitions.

⚠️ PLAYWRIGHT USERS: READ "CRITICAL: Playwright Browser Session Behavior" SECTION BELOW!

Each MCP call = new browser session. Browser CLOSES after each call. You CANNOT navigate in one call and click in another. Use browser_run_code for ANY multi-step operation. If you need to return to a state (e.g., logged in), you MUST redo ALL steps from scratch.

How It Works

Instead of loading all MCP tool schemas into context, this client:

1. Lists available servers from config
2. Queries tool schemas on-demand
3. Executes tools with JSON arguments

Configuration

Config location priority:

1. MCP_CONFIG_PATH environment variable
2. .claude/skills/mcp-client/references/mcp-config.json
3. .mcp.json in current directory
4. ~/.claude.json

Commands

# List configured servers
python scripts/mcp_client.py servers

# List tools from a specific server
python scripts/mcp_client.py tools playwright

# Call a tool
python scripts/mcp_client.py call playwright browser_navigate '{"url": "https://example.com"}'

---

CRITICAL: Playwright Browser Session Behavior

⚠️ The Session Problem

Each MCP call creates a NEW browser session. The browser CLOSES after each call.

This means:

# ❌ WRONG - These run in SEPARATE browser sessions!
python scripts/mcp_client.py call playwright browser_navigate '{"url": "https://example.com"}'
python scripts/mcp_client.py call playwright browser_click '{"element": "Accept cookies"}'
python scripts/mcp_client.py call playwright browser_snapshot '{}'
# ^ The snapshot captures a FRESH page, not the page after clicking!

✅ The Solution: browser_run_code

Use browser_run_code to run multiple Playwright steps in ONE browser session:

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://example.com\");

    // Wait for and click cookie banner
    const acceptBtn = page.getByRole(\"button\", { name: /accept/i });
    if (await acceptBtn.isVisible({ timeout: 3000 }).catch(() => false)) {
      await acceptBtn.click();
      await page.waitForTimeout(1000);
    }

    // Wait for page to stabilize
    await page.waitForLoadState(\"networkidle\");

    // Return snapshot data for analysis
    const snapshot = await page.accessibility.snapshot();
    return JSON.stringify(snapshot, null, 2);
  "
}'

When to Use Each Approach

Scenario	Tool	Why
Simple page load + snapshot	browser_navigate	Returns snapshot automatically
Multi-step interaction	browser_run_code	Keeps session alive
Click then observe result	browser_run_code	Session persists
Fill form and submit	browser_run_code	Session persists
Hover to reveal menu	browser_run_code	Session persists

---

Playwright Workflows for Test Discovery

1. Basic Page Exploration (Single Step)

browser_navigate returns both navigation result AND accessibility snapshot:

python scripts/mcp_client.py call playwright browser_navigate '{"url": "https://example.com"}'

Output includes:

• Page URL and title
• Full accessibility tree (all visible elements with roles, names, states)
• Element references for further interaction

Use this when: Simple page load without interactions

2. Page with Cookie Banner (Multi-Step)

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://www.olx.ro\");

    // Handle cookie consent
    try {
      const cookieBtn = page.getByRole(\"button\", { name: \"Accept\" });
      await cookieBtn.click({ timeout: 5000 });
      await page.waitForTimeout(1000);
    } catch (e) {
      // No cookie banner
    }

    // Get accessibility snapshot
    const snapshot = await page.accessibility.snapshot({ interestingOnly: false });
    return JSON.stringify(snapshot, null, 2);
  "
}'

3. Navigate to Subpage (Multi-Step)

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://www.olx.ro\");

    // Dismiss cookies
    const acceptBtn = page.getByRole(\"button\", { name: \"Accept\" });
    if (await acceptBtn.isVisible({ timeout: 3000 }).catch(() => false)) {
      await acceptBtn.click();
      await page.waitForTimeout(500);
    }

    // Navigate to login
    await page.goto(\"https://www.olx.ro/cont/\");

    // Wait for redirect to login domain
    await page.waitForURL(/login\\.olx\\.ro/, { timeout: 10000 });

    // Get form structure
    const snapshot = await page.accessibility.snapshot();
    return JSON.stringify({ url: page.url(), snapshot }, null, 2);
  "
}'

4. Explore Element Interactions (Multi-Step)

Use this to understand how menus/dropdowns behave:

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://www.olx.ro\");

    // Dismiss cookies
    const acceptBtn = page.getByRole(\"button\", { name: \"Accept\" });
    if (await acceptBtn.isVisible({ timeout: 3000 }).catch(() => false)) {
      await acceptBtn.click();
    }

    // Click on category to see what happens
    const categoryLink = page.getByRole(\"link\", { name: /Auto, moto/i }).first();
    await categoryLink.click();

    // Wait to see result
    await page.waitForTimeout(1500);

    // Capture state after click
    const snapshot = await page.accessibility.snapshot();
    return JSON.stringify({
      url: page.url(),
      didNavigate: page.url().includes(\"auto\"),
      snapshot: snapshot
    }, null, 2);
  "
}'

5. Fill Form and Capture State

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://login.olx.ro\");

    // Fill login form
    await page.locator(\"input[type=email]\").fill(\"test@example.com\");
    await page.locator(\"input[type=password]\").fill(\"test123\");

    // Click login button
    await page.getByTestId(\"login-submit-button\").click();

    // Wait for response
    await page.waitForTimeout(3000);

    // Capture any error messages
    const errors = await page.locator(\"[class*=error], [role=alert]\").allTextContents();
    const snapshot = await page.accessibility.snapshot();

    return JSON.stringify({
      url: page.url(),
      errors: errors,
      snapshot: snapshot
    }, null, 2);
  "
}'

---

Gathering Selectors for Page Objects

Best Practices

1. Use Accessibility Tree First

The snapshot from browser_navigate or browser_run_code provides:

• Role: button, link, textbox, combobox, etc.
• Name: accessible name (from label, aria-label, text content)
• State: disabled, checked, expanded, etc.

Map these to Playwright locators:

// From snapshot: { role: "button", name: "Căutare" }
page.getByRole('button', { name: /Căutare/i })

// From snapshot: { role: "textbox", name: "Ce anume cauți?" }
page.getByRole('textbox', { name: /Ce anume cauți/i })

// From snapshot: { role: "link", name: "Auto, moto și ambarcațiuni" }
page.getByRole('link', { name: /Auto, moto/i })

2. Selector Priority

Priority	Method	Use When
1	getByRole()	Element has semantic role + accessible name
2	getByTestId()	Element has data-testid attribute
3	getByText()	Unique text content
4	getByPlaceholder()	Input with placeholder
5	locator('[attr="value"]')	CSS attribute selector
6	locator('.class')	CSS class (fragile, avoid)

3. Handling Multiple Matches

// Use .first() when multiple match
page.getByRole('link', { name: 'Category' }).first()

// Use parent context
page.locator('nav').getByRole('link', { name: 'Category' })

// Use filter
page.getByRole('button').filter({ hasText: /submit/i })

4. Get Full DOM for Complex Cases

When accessibility tree isn't enough, get raw HTML:

python scripts/mcp_client.py call playwright browser_run_code '{
  "code": "
    await page.goto(\"https://example.com\");

    // Get specific element HTML
    const formHtml = await page.locator(\"form\").first().innerHTML();

    // Or get all buttons with their attributes
    const buttons = await page.locator(\"button\").evaluateAll(btns =>
      btns.map(b => ({
        text: b.textContent,
        testid: b.dataset.testid,
        class: b.className,
        type: b.type
      }))
    );

    return JSON.stringify({ formHtml, buttons }, null, 2);
  "
}'

---

Quick Reference: Playwright MCP Tools

Tool	Session Behavior	Use Case
browser_navigate	New session, returns snapshot	Simple page load
browser_run_code	Single session, custom script	Multi-step operations
browser_click	New session	Single click (usually not useful alone)
browser_type	New session	Single type (usually not useful alone)
browser_snapshot	Reuses if session exists	Get current page state
browser_screenshot	Reuses if session exists	Visual capture

Tool Arguments

browser_navigate

{"url": "https://example.com"}

browser_run_code

{
  "code": "await page.goto('https://example.com'); return await page.title();"
}

The code must be valid JavaScript that:

• Uses page object (Playwright Page)
• Uses await for async operations
• Returns the data you want (use JSON.stringify for objects)

browser_click

{"element": "Submit button", "ref": "optional-element-ref"}

browser_type

{"element": "Email input", "text": "user@example.com"}

---

Error Handling

Error	Cause	Fix
"No MCP config found"	Missing config file	Create mcp-config.json
"Server not found"	Server not in config	Add server to config
"Connection failed"	Server not running	Start the MCP server
"Invalid JSON"	Bad tool arguments	Check argument format
"Timeout"	Page too slow	Increase timeout in code
"Element not found"	Wrong selector	Check snapshot for actual names

---

Setup

1. Copy the example config:

   cp .claude/skills/mcp-client/references/mcp-config.example.json \
      .claude/skills/mcp-client/references/mcp-config.json
   

2. The config should contain:

   {
     "mcpServers": {
       "playwright": {
         "command": "npx",
         "args": ["@playwright/mcp@latest"]
       }
     }
   }
   

3. Install dependencies:

   pip install mcp fastmcp
   

Config Example

See references/mcp-config.example.json

Available Servers

See references/mcp-servers.md for:

• Playwright (browser automation)
• GitHub (repository operations)
• Filesystem (file access)
• Sequential Thinking (reasoning)
• And more...

Dependencies

pip install mcp fastmcp