The State of MCP Reliability
April 2026
The first independent assessment of reliability, security, and maintenance across the MCP server ecosystem
Executive Summary
Key Findings
27% of remote MCP endpoints are dead. Out of 2,181 remote-capable servers, 582 fail to respond — timeout, connection refused, or not found.
298 servers (13.7%) have zero authentication. Any agent can connect and execute tools without credentials.
52% have open CORS (Access-Control-Allow-Origin: *), allowing cross-origin requests from any domain.
Finance scores lowest on trust despite handling the most sensitive data — a notable gap between risk and security posture.
Ecosystem Overview
YellowMCP indexes 20,348 MCP servers from the Official MCP Registry, Smithery, PulseMCP, mcpmonitoring.com, and community lists. Of these, 2,181 have remote endpoints that can be independently monitored.
Data Sources
Category Distribution
Reliability Assessment
Server Status (2,181 remote endpoints)
30-Day Uptime Distribution
Latency Distribution
Top 10 Most Reliable Servers
| # | Server | Category | Uptime | Latency | Trust |
|---|---|---|---|---|---|
| 1 | PostHog MCP Server★32,537 | dev-tools | 99.8% | 535ms | 100 |
| 2 | edgar.tools SEC Intelligence★1,990 | dev-tools | 99.2% | 541ms | 95 |
| 3 | Buildkite★50 | dev-tools | 99.6% | 653ms | 95 |
| 4 | io.github.alphavantage/alpha_vantage_mcp★119 | dev-tools | 99.9% | 635ms | 85 |
| 5 | ai.smithery/brave★891 | dev-tools | 99.9% | 681ms | 95 |
| 6 | com.monday/monday.com★394 | dev-tools | 99.7% | 657ms | 100 |
| 7 | ai.smithery/docfork-mcp★459 | dev-tools | 99.8% | 695ms | 95 |
| 8 | Slack MCP Server★21 | dev-tools | 99.7% | 591ms | 100 |
| 9 | Axiom★11 | data | 99.4% | 684ms | 100 |
| 10 | com.stripe/mcp★1,456 | finance | 99.2% | 799ms | 95 |
Security Intelligence
2,180 remote MCP servers scanned with 5 passive security checks: authentication, transport security, CORS policy, information leakage, and SSL/TLS certificate quality.
Trust Score Distribution
298 servers have zero authentication
13.7% of remote MCP servers respond with 2xx and no authentication required. Any agent can connect and execute tools without credentials. This is the #1 security concern in the ecosystem.
Authentication
SSL/TLS Certificates
Trust Score by Category
Maintenance & Activity
Of 1,206 remote servers with linked GitHub repositories, only 40% have committed code in the last 30 days. Abandoned MCP servers represent a growing reliability risk — they accumulate security vulnerabilities and drift from protocol updates.
Methodology
Health Monitoring
Every remote endpoint is checked via HTTP GET/SSE handshake every 5-15 minutes. We record status code, response latency, and error details. Servers are classified as up (2xx within 10s), degraded (slow or intermittent), reachable (401/403), or down (timeout/error).
Security Scanning
All checks are passive and non-intrusive. We assess authentication requirements, transport security (HTTPS), CORS headers, information leakage (server headers, error details), and SSL certificate validity. No penetration testing or active exploitation.
Trust Score
Starts at 100. Deductions: no authentication (-30), HTTP only (-25), invalid SSL (-20), expiring SSL (-10), weak auth (-10), error details exposed (-10), open CORS (-5), server headers exposed (-5), low uptime (-10 to -30). Range: 0-100.
Limitations
Uptime data reflects only the monitoring period (since April 1, 2026). Servers without remote endpoints cannot be health-checked. Security scans assess external posture only — internal architecture and code quality are not evaluated. Trust scores are not endorsements.
Recommendations
For developers choosing MCP servers
Check uptime history before depending on a server. Verify it requires authentication. Look at GitHub commit activity — a server with no commits in 90 days is a maintenance risk. Use YellowMCP's agent discovery tools to find reliable servers at runtime.
For MCP server operators
Claim your listing on YellowMCP to verify ownership. Add authentication — 13.8% of the ecosystem is wide open. Monitor your uptime and set up alerts. Embed a reliability badge in your README to signal quality.
For the ecosystem
The MCP ecosystem has a quality layer problem. Registries list servers but don't verify they work. Discovery tools don't assess security. The gap between “listed” and “production-ready” is where reliability intelligence fits.
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