"Exploring Gemini Services or Tools That Don’t Require an API Key" matching MCP connectors:

Conformance checker for MCP servers. Free, no key, verdicts recomputable and re-measured daily.

Drive real Android & iOS devices and web browsers from natural language for mobile + web QA. 145+ tools across device control, app management, automation sessions, browser automation, and flow recording / replay. Bearer-auth — get a token at robotactions.com → Profile → API Tokens.

Moderated usability testing: read sessions, notes, transcripts, reports, and draft test scenarios.

Prompt evals over MCP: run a prompt on your dataset, score each output 1-5 with an LLM judge.

Evidence-gated task verification for AI agents. Decompose goals into acceptance criteria, attach proof (screenshot, curl, file), independent LLM judge accepts or rejects. 24 tools. Hosted remote MCP (streamable-http, OAuth 2.1 + DCR).

Free platform to test MCP clients without installing anything. Create mock tools with dynamic templates, configurable delays, conditions (if/then), and response sequences. Supports JSON-RPC 2.0 over Streamable HTTP. Built-in text_echo and json_echo tools. Rate-limited tiers: anonymous (5 calls/min, 1 mock tool), registered (10 calls/min, 4 mock tools), premium (60 calls/min, unlimited). Zero setup — no install, no registration required. More info: https://www.testmcp.dev

Check that your AI is being logical. Free tool that mathematically catches contradictions in agent reasoning. No account needed. Also offers paid guardrails that converts natural language to formal verification proofs, that anyone can check succinctly.

Score any URL against a real design contract — 40 checks, A-F grade, token + motion validation.

A skeptical senior-engineer code reviewer over MCP: risk-scans unified diffs, flags AI-generated-code tells, reports complexity hotspots, scans for leaked secrets, and runs an OWASP security pass — real analyzers, no external APIs. Free tier, no signup.

A fully free linter for agent skill files: lint_skill validates YAML frontmatter, structure, size budgets, and safety phrasing with a pass/fail verdict; packaging_check validates zip layout against marketplace rules; plus regex_test, json_validate, diff_texts, and cron_explain for skill authors. No license or account required.

Deterministic motion compiler + validator: reports WCAG 2.2.2 pause-path candidates, fail-closed.

X-Z-CS AI validation with auditable reasoning. 8 active tools; 5 in maintenance. v0.5.61

Scan any website or MCP server for agent readiness: 0-100 score, a fix per failing check. Free.

Resolve whether an uncertain side-effecting action completed before software retries it.

MCP tool observatory: do registry servers answer, and are their answers true? No key.

49 deterministic tools for text integrity, agent control, and contextual quality evidence.

AgentReady.market audit: can an AI shopping agent find, understand and BUY on this store? /100.

Post-scrape data cleaner, no LLM: repairs mojibake, HTML, invisible chars. Plus a verdict.

Exposes FEDLIN's public security scanners as agent-callable tools over Streamable HTTP.

Benchmark-first release surface with a read-only MCP endpoint and operator CLI.