"Free APIs and services without commercial fees" matching MCP servers:

Enables users to create, validate, view, and export system stock-and-flow maps from a versioned JSON model through MCP-capable hosts over local stdio or hosted Streamable HTTP. Supports causal-loop and nested-level mapping while keeping submitted model content with the caller and requiring no LLM provider key.

Offline MCP server for SAP ABAP static analysis, ABAP Cloud readiness scoring, and RAP scaffolding. It enables AI agents to lint ABAP source, compare reworks, check released APIs, and generate RAP business objects without needing an SAP system.

Enables rendering, validation, formatting, and inspection of D2 diagrams via the Model Context Protocol, using WASM for rendering without requiring the d2 binary.

A read-only MCP server that gives AI agents access to Sparx Enterprise Architect models, enabling search, navigation, and reading of elements, packages, scenarios, and connectors from .qea exports without a running EA instance.

Model Context Protocol (MCP) server for @imqueue — lets AI coding agents (Claude Code, Cursor and others) search the docs, scaffold typed services & clients and use @imqueue/cli live.

AI-native architecture diagramming for MCP clients (Claude Code, Cursor, Windsurf). The calling agent authors the graph (nodes, groups, edges); Flowgraf validates it, lays it out deterministically with ELK, renders an SVG + Mermaid, and returns a link to a live, editable canvas you can refine by chat, drag, or one-click AI design review. Agent-authored ops — no API key and no LLM cost to the calle

Renders diagram-as-code to PNG files on your disk, and also provides text-art previews and syntax validation, all locally without a browser or network.

A research proxy that lets Claude, Cursor, and other MCP clients utilize Gemini's generous free tier for deep codebase analysis without burning your main model's quota!

A graph layout server that computes node coordinates and edge paths from structure using elkjs, enabling agents to offload layout calculations without rendering.

An MCP server that exposes a Svelte/SvelteKit project's component dependency graph over stdio, enabling AI coding assistants to query component imports, unused components, and route dependencies without an editor.

Extracts deterministic architecture maps from codebases for AI agents, enabling queries about blast radius, routes, security findings, and production readiness without sending code anywhere.

An MCP server that recommends tech stacks for your project. Describe what you're building and get a recommended stack with reasoning, tradeoffs, and what each layer should use.

Exposes read-only Huly task intake, architecture guidance, UX patterns, and static validators through eight MCP tools, letting host agents drive approval-gated Flutter and Frappe delivery workflows. It can also be inspected directly (e.g. via the MCP inspector) so users can exercise the tools without an agent.

Enables AI assistants to understand and analyze Spring Boot codebases through static analysis, allowing natural language queries about endpoints, classes, dependencies, and architecture without running the application.

MCP server that creates, edits and exports architecture diagrams as .fluyo.json files, operating through tools like create_diagram, edit_diagram, and export_diagram directly from Claude.

Tech stack recommendations for developers. Deterministic 6-dimension scoring across 30+ technologies. 4 free tools, Pro features with API key.

Enables AI agents to edit diagram/graph structures on a live draw.io canvas and manage local versions via snapshots, restore, and export without embedding a separate LLM or polluting the workspace.

A lightweight sketch canvas that lets users draw ideas and sync them in real-time to AI via MCP, enabling visual communication without exports.

Cross-repository code knowledge graph MCP server for Java, Kotlin, JavaScript, and TypeScript. Indexes source code into embedded KuzuDB via tree-sitter and exposes 30+ tools for call-flow tracing, multi-hop taint analysis (OWASP/CWE/PCI/STIG), entry-point reachability filtering, performance hotspot detection, and license compliance — without reading source files. 95% fewer tokens vs source-read

Enables agents and IDEs to generate and verify NestJS microservices with hexagonal architecture, JSON:API contracts, and mandatory security headers. Supports declarative spec-based module generation, refactoring existing services, quality checks, and per-repository inventory and auditing.

This MCP server enables AI models to analyze local Python codebases using abstract syntax trees, providing tools for file structure analysis, symbol search, import graphing, docstring auditing, and refactoring prompts without loading entire source files into context.

Score your agent's governance (0-100), lint MCP tool definitions, and estimate costs across all major models. Free diagnostic tools with no API key needed. Expert skill files on governance, economics, and system architecture available with free tier.

Enables MCP clients to scope and generate safe Odoo add-on starters locally, including drafting architecture plans, creating 11-file add-on scaffolds, validating them, and saving files to disk—all without API keys or network access.

Turns Claude or ChatGPT into a live system design interviewer that watches a hand-drawn whiteboard, reads the diagram as structured data or an image, hears spoken answers, pins questions on components, and grades the session. Everything runs locally, so users can practice mock interviews on their own machine without API keys.

Parses Mermaid ER diagrams to create PostgreSQL tables and automatically generates REST and GraphQL CRUD APIs.

Generates complete, production-ready REST, GraphQL, and microservice APIs with built-in security, validation, and deployment configurations.

A training MCP server that demonstrates how GitHub Copilot can securely access internal banking APIs, documentation, and architecture review prompts.

Automatically generates compelling application specifications and code based on the four dimensions (existence, historicity, relationality, irrationality), simplicity, and Figma-like UI, enabling users to create great apps without detailed instructions.

Enables AI agents to generate BYaML Architecture Graphs from evaluations, Terraform plans, and AWS scans, and to derive insights such as blast radius, cost summaries, and remediation plans without writing YAML.

A design orchestrator that brings Superdesign capabilities to Claude Code as native tools, enabling AI-powered UI design, wireframing, component creation, and logo/icon generation without requiring Anthropic API keys.