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majiayu000/claude-skill-registry/mcp-client

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PublishedMay 15, 2026 at 10:57 PM

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version: "1.0.1" name: mcp-client description: Universal MCP client for connecting to any MCP server with progressive disclosure. Wraps MCP servers as skills to avoid context window bloat from tool definitions. Use when interacting with external MCP servers (Playwright, GitHub, filesystem, etc.), listing available tools, or executing MCP tool calls. Triggers on "connect to MCP", "list MCP tools", "call MCP", "use Playwright", "browser navigate", "browser snapshot".

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:

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

Configuration

Config location priority:

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

Commands

bash

# 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:

bash

# ❌ 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:

bash

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:

bash

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)

bash

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)

bash

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:

bash

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

bash

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:

typescript

// 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

typescript

// 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:

bash

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

json

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

browser_run_code

json

{
  "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

json

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

browser_type

json

{"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

Copy the example config:

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

The config should contain:

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

Install dependencies:

``bash 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

bash

pip install mcp fastmcp

← v1.0.0 All versions

Skill v1.0.1

Universal MCP Client

How It Works

Configuration

Commands

CRITICAL: Playwright Browser Session Behavior

⚠️ The Session Problem

✅ The Solution: browser_run_code

When to Use Each Approach

Playwright Workflows for Test Discovery

1. Basic Page Exploration (Single Step)

2. Page with Cookie Banner (Multi-Step)

3. Navigate to Subpage (Multi-Step)

4. Explore Element Interactions (Multi-Step)

5. Fill Form and Capture State

Gathering Selectors for Page Objects

Best Practices

1. Use Accessibility Tree First

2. Selector Priority

3. Handling Multiple Matches

4. Get Full DOM for Complex Cases

Quick Reference: Playwright MCP Tools

Tool Arguments

browser_navigate

browser_run_code

browser_click

browser_type

Error Handling

Setup

Config Example

Available Servers

Dependencies

✅ The Solution: `browser_run_code`