"Understanding Prompts or Prompt Engineering" matching MCP connectors:

Connect Claude or any MCP client to Thread Otter, a GTM agent for founders. Free tools with no key: find_buyer_threads (give it a website URL and get recent Reddit threads where that product's buyers are asking for it, report in ~3 minutes), reddit_demand_board (weekly demand across 40 communities with thread receipts), and subreddit_rules (promotion posture for 2,000+ profiled subreddits). With an API key: read your buying-intent mentions across Reddit, X, LinkedIn, and Bluesky, check your pipeline, and propose posts and reply drafts in your voice. Propose-only by design: nothing sends without your approval flow. Keys at threadotter.com/connect.

Open AI Visibility Index for crypto and Web3. Weekly share-of-answer measurements for 24 tracked brands across ChatGPT, Perplexity and Gemini, from a frozen versioned prompt panel. Five read-only tools: full index, per-brand lookup, brand list, complete measurement history and methodology. No auth, no API key. Data is CC BY 4.0 with a permanent archive of every weekly snapshot, so any figure can be verified independently.

Open AI Visibility Index for SaaS and AI tools. Weekly share-of-answer measurements for 20 tracked brands across ChatGPT, Perplexity and Gemini, from a frozen versioned prompt panel. Five read-only tools: full index, per-brand lookup, brand list, complete measurement history and methodology. No auth, no API key. Data is CC BY 4.0 with a permanent archive of every weekly snapshot, so any figure can be verified independently.

Open scientific and engineering knowledge for AI agents: search, evidence, document publishing.

An MCP server that gives any LLM or agent clean YouTube transcripts on demand: a single video, a whole channel, or a playlist, plus AI cleanup of auto-generated captions. API-key auth, credit-based, same backend as the public v1 API. Get a free API key with 25 free credits at youtubetranscriptdownload.com/account.

Connect Claude, Cursor or any MCP client to AppSigma and let your AI research apps, read reviews and track rankings on its own – no glue code.

Docs: https://docs.keenable.ai/mcp-server Keenable is a free, remote MCP server that gives agents access to the web index. Search the web with ranked results and date/site filters, then fetch any indexed page as clean markdown. Works out of the box with no account or API key.

Image + screenshot API for agents: HTML/CSS to images or PDF, screenshot any URL, verify text.

Amazon brand, seller, niche & buy-box intelligence inside your own Claude or ChatGPT.

Scrape, crawl, map and extract the web. Pay per call in USDC, no account or API key.

Probability prose is AI-written, with the tells behind the score. No API key — text or URL in.

SEC EDGAR fundamentals as agent tools: look up or screen US public companies. Free, no key, CC0.

Read-only scripture-study engine: complete-or-fail concordance over Greek NT, Hebrew OT, LXX.

Query an independent, payment-blind reference of 1,682 dermacosmetic products — by product, ingredient, concern, category or brand. Neutral descriptive facts, every result links back to its reference page. No ratings, no paid placement.

Read-only live geopolitical-risk sensing for agents. ARCANE notices; never forecasts or advises.

88 free engineering calculators: RF link budgets, LoRa/Meshtastic, PCB, solar, homelab. Keyless.

Find products & standards using a patent - verified targets for licensing or enforcement.

Public read-only Précis Finance MCP demo with synthetic data; no account or credentials required.

Citation-health over a CC0 citation graph: what supports, refutes, or cites a paper. Read-only.

Screen a vendor, store, or group-buy for legitimacy: reputation, red flags, Reddit sentiment.