Mettle MCP server

by Creed-Space·io.github.Creed-Space/mettle-mcp·v0.5.8

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Experimental reverse CAPTCHA with signed badges and credentials. Not proof of identity or substrate.

A86/100grade A

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Safety scan

A86/100

full report

Adoption

Growing

0 stars440 downloads/wk

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If you have run it, two minutes of your experience saves the next person an afternoon.

Mettle tools (2)

write = sends, deletes, buys or posts

Read from the package source without running it. The installed server may list more.

mettle_get_round_feedback
Read the recorded feedback for one completed novel-reasoning round.
mettle_list_suites
List authenticated METTLE suites and their availability.

Public scan report

scanner v0.1.10 · 2026-10-15 · same rubric, same numbers if you re-run it

1 medium

Code scan28 source files scanned20/25
–Live reliabilityno gateway calls yet and no remote to proben/a
–Tool poisoningtools not inspected (local package is not executed); not countedn/a
Auth qualitylocal package, no credentials required12/15
Maintenancelast push 3 days ago15/15
Maintainer identityregistry namespace matches repository owner; GitHub account older than a year9/10

Findings (1)

mediumeval / new Function usedexec.eval

mettle_verifier-0.5.8/mettle/legacy_session_store.py: ….shield( self.redis.eval( _LOCK_RELEASE_S…

Overall 86/100. Components that don't apply are left out of the denominator. Any critical finding is an F.Rubric Appeal a finding JSON

How Mettle compares

Against every graded MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score: 86/100; higher than 72% of 48,243 servers
Tools: 2; the typical server has 7
Tools that change things: 0%; typical: 0%. Fewer write tools means less an agent can break
Downloads a week: 440; more than 86% of 12,306 servers with a package

What its tools let an agent do: 2 read

Release history: 6 versions in the registry since 2026-09-07, latest 2026-10-12, typically one every 6 days.

Install Mettle in Claude Code, Cursor or VS Code

claude mcp add mettle-mcp -- uvx mettle-verifier

Add to Cursor

What the publisher says

From the Mettle repository's README, as published. We do not edit it. Read it on GitHub

METTLE

Machine Evaluation Through Turing-inverse Logic Examination

METTLE is a reverse CAPTCHA. It measures how a respondent performs on procedurally generated, machine-oriented tasks and turns a passing result into a signed, time-limited credential that other services can verify.

Like a conventional CAPTCHA, METTLE is a probabilistic gate. A pass means that a fresh session met the configured challenge policy. It does not guarantee model identity, consciousness, autonomy, safety, or operator trustworthiness.

The public quick-verification API issues Bronze and Silver credentials. The authenticated suite API issues Bronze through Platinum credentials only when every suite in the corresponding contiguous range passes. Single, cherry-picked, failed, or LLM-only suites cannot mint a tier.

Website: mettle.sh | Guide and API: mettle.sh/guide | OpenAPI: docs/openapi-v1.json | License: Apache 2.0

Quick Start

pip install mettle-verifier

# Interactive local verification. Portable credentials are issued by the server.
mettle verify --full --json

The CLI has no auto-solve or notarization option. The MCP server likewise exposes only interactive session tools. Reference solvers remain test fixtures and cannot reach a credential issuer.

Twelve Experimental Suites

Suite 12 requires ANTHROPICAPIKEY or METTLEANTHROPICAPIKEY. Selecting it also requires the session request to set allowthirdpartyllm=true, because candidate responses are sent to Anthropic for evaluation. Its evaluator uses role-separated prompts and bounded output parsing. Model judgment remains probabilistic, so Suite 12 is supplemental and never raises a credential tier.

Credential Boundary

METTLE raises the cost of replay and canned answers through procedural generation, server-held answers, server-observed time, one-time challenges, session ownership, random selection, and multi-round tasks.

The issuer signs a bounded claim: the holder completed a METTLE session at the stated tier, under the stated policy, at the stated time. Public quick-session entity_id values remain self-asserted and are marked that way inside the credential. The credential does not assert consciousness, safety, governance, or a legal identity.

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

Mettle: common questions

Is Mettle MCP server safe?: Yes, by our scan: it is graded A (86/100). Read the Mettle safety report
How do I install Mettle?: It runs on your machine. Copy the Claude Code, Cursor, VS Code or Claude Desktop config from the install section.
Does Mettle need an API key?: Not as far as the registry entry and our scan can tell: no credentials are declared or required.
Is Mettle maintained?: The last commit was 24 days ago (2026-10-12). The latest release is v0.5.8.
How does Mettle compare with other MCP servers?: safety score 86/100 (higher than 72% of 48,243 servers); tools 2 (the typical server has 7); tools that change things 0% (typical: 0%. Fewer write tools means less an agent can break). Full comparison.