"Tools for visualizing NetworkX graphs without an API key" matching MCP servers:

Human-in-the-loop approval: a person approves the exact AI action with a passkey, and any service can check the signed approval offline.

Enables creation and management of state/decision graphs using NetworkX, supporting directed graphs with conditional branches, edge ordering, path finding, and visualization through PNG exports or interactive web interface.

A comprehensive suite of HTTP and API testing tools that enables AI agents to perform requests, check endpoint health, and decode JWTs. It also provides utilities for URL parsing and detailed security analysis of HTTP response headers.

Enables Tavily and Firecrawl MCP servers to operate with multiple API keys, automatically rotating to backup keys on quota exhaustion, rate limits, or invalid keys, while rewriting API endpoints to the local proxy.

Full-stack utility API with 337+ tools including AI chat, web scraping, weather, finance, SEO, crypto, colors, readability, DNS, and more — all through a single MCP server. Pay-as-you-go credits, no API keys needed.

Enables users to register a single one-line secret credential (such as a personal access token) that is stored encrypted and scoped to their exact user and persona pair, then let MCP tools retrieve and use that key to call an upstream service. Key names can be listed for status checks, but the secret value itself is only decrypted inside a tool at call time.

A local MCP server that enables AI applications like Claude Desktop to securely access and work with Obsidian vaults, providing capabilities for reading notes, executing templates, and performing semantic searches.

MCP server for Cursor IDE offering tools for Human Design chart analysis, partner matching, n8n workflow management, and utility functions like UUID generation and calculation.

Free Industry 4.0 / IIoT tools, no API key or account: lint MQTT Sparkplug B topics, check a Unified Namespace (UNS) for naming and hierarchy problems, and run an industrial AI-readiness diagnostic for manufacturing digital transformation and smart-factory projects. Works in Claude Code, Codex and any MCP client.

MCP server that exposes tools to route natural language queries to typed IDs, describe catalog entries, and list repository verification commands for the m-dev-tools organization.

Enables validating JSON/JSONC, getting/setting values with jq-like paths, pretty-printing or minifying, validating against Ajv JSON Schema, and diffing local files or inline strings without network calls.

Enables AI agents to pay per call for live package-safety and GitHub merge-readiness trust signals via the x402 protocol.

Provides 13 offline SEO and marketing tools to any MCP client, covering ad metric calculators, text and heading analysis, keyword density, and generators for meta tags, Open Graph, hreflang, schema markup, XML sitemaps, and robots.txt. Everything runs locally with no account, API key, or network calls.

Exposes AWS Palace finite-element electromagnetic simulation as a set of JSON-in/JSON-out tools, so an agent can build geometry and meshes, generate and lint configs, estimate cost, guard and launch runs, and read back S-parameters, eigenmodes, Q and energy results. Results return as JSON text plus structured content over a dependency-free stdio JSON-RPC connection.

Provides computational tools for systematic reasoning, including boolean evaluation, date arithmetic, object counting, state tracking, and format validation, to enhance agent capabilities and eliminate calculation errors in reasoning tasks.

Provides AI-powered tools to apply UX/UI best practices, Nielsen's heuristics, cognitive biases, and Material-UI patterns to React components. Enables automated application of responsive design, Apple design patterns, and complete UX guidelines through natural language commands.

Offers 29 free tools for text processing, AI-powered generation, SEO optimization, utilities, cron tasks, file processing, and ideas management, all without requiring an API key.

Turn any API into an MCP server. Query in English. Get results—even when the API can't.

A remote MCP server that lets AI agents generate PDFs from Markdown or HTML, extract text from images and PDFs, validate and screen email addresses, convert or host images, and create QR codes and barcodes. It also exposes account, subscription, and API-discovery tools, with every call running against the same REST quotas tied to the caller's own API key.

Provides deterministic tools for transforming, formatting, and inspecting structured data for AI agents.