MCP Score
The MCP Score is CheckMCP's vendor-neutral, explainable 0–100 grade for a Model Context Protocol server. It combines seven weighted pillars — security, tool design, schemas, reliability, context-cost, compliance and coverage — into one number, and attributes every deduction as measure → mechanism → effect, so the score is auditable rather than a black box.
The seven pillars
Each pillar measures one dimension of server quality: security (an OWASP MCP Top 10 pass, the top-weighted pillar), tool design (sprawl vs. consolidation, calibrated on real servers), schemas & descriptions (tool and input/output schema completeness), context-cost (tokens paid on every tools/list), compliance (protocol-version gap, annotations, JSON-RPC error conformance, OAuth discovery), reliability (drift over time), and coverage (tools, resources and prompts).
The pillars are weighted and summed to a 0–100 score, then mapped to a letter grade.
Hard floors
Some problems are categorical, not gradual. A hardcoded secret in a schema or a critical injection (tool poisoning) caps the grade at D no matter how clean the rest is; a failed protocol handshake caps it at F. These floors stop a server from buying back a serious security failure with polish elsewhere.
Explainable, and more than the endpoint
Every penalty is traceable: the report states what was measured, the mechanism, the effect on the agent, and the points lost — Lighthouse-style. CheckMCP also grades the backing GitHub repository separately as a Repo-Quality Score /100 (maintenance, license, adoption, documentation), so a server is judged on both its live behavior and its project health.
How CheckMCP handles it
The MCP Score is what CheckMCP produces for every audited server. It is computed in the open (the methodology is published), calibrated on a growing corpus of real MCP servers, and free — you get it by pasting a URL at checkmcp.dev or running the CLI. The score stays free as the acquisition layer; paid plans add continuous monitoring, behavioral evals and the in-band gateway.