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MCP server for MicroTap (x402tap.com) — 20 pay-per-call x402 APIs (prediction markets, DeFi, crypto, multi-chain on-chain data, weather, web search). Install into Claude Desktop, Claude Code, Cursor, or Windsurf; pay per call in USDC on Base, no signup or API key.
The server defines 19 tools with explicit routing and Zod schema definitions visible in src/tools.ts. Tool names follow verb-noun patterns (get_, search_, find_, call_, rank_) which is correct. Descriptions are present for all tools and include pricing information, which is helpful for agent decision-making. However, several issues reduce quality: (1) Many tools lack complete input schema validation, parameters use Zod but the actual runtime validation and error messages are not visible; (2) Output schemas are completely undocumented, no TypeScript interfaces or JSON Schema definitions are shown for responses, forcing agents to guess response structure; (3) Parameter descriptions are often generic ('e.g. bitcoin,ethereum') rather than prescriptive, with examples embedded instead of formal constraints; (4) Some parameters lack basic metadata (minValue, maxValue, pattern); (5) No error recovery guidance visible, tools don't appear to return actionable error messages; (6) Security and audit logging patterns not evident in the visible code. The server does use TypeScript with Zod for compile-time safety, which is a positive sign, but the MCP interface layer (what agents actually see) is not sufficiently detailed.
Safelisted read-only JSON-RPC proxy across Base, Ethereum, Polygon, Arbitrum, and Optimism — eth_call, eth_getBalance, eth_getTransactionReceipt, eth_blockNumber, and more. Write methods (sending transactions, signing) are never permitted. Price: $0.003 per call.
Finds prediction-market questions priced differently on Polymarket vs. Kalshi — a cross-platform divergence signal built from data no single-platform competitor has. Matches are keyword-overlap similarity, not a verified same-event guarantee; sanity-check a match before treating it as a real arbitrage signal. Price: $0.005 per call.
Generates short text output for a prompt. Billed by output length, up to $0.05 max per call (x402 'upto' scheme — you authorize a ceiling, the actual charge is based on what's produced). Price: usage-based, max $0.05 per call.
Rich market data for one or more cryptocurrencies: rank, 24h high/low, volume, all-time high, and more. Price: $0.002 per call.
Current price, 24h change percent, and market cap for one or more cryptocurrencies. Price: $0.001 per call.
No output schemas documented. Tools define no TypeScript interfaces or JSON Schema for response structures. Agents cannot plan downstream tool calls or validate responses without this documentation.
Parameter descriptions contain example values ('e.g. bitcoin,ethereum', 'e.g. Austin') instead of formal constraints. LLMs latch onto examples and may pass them literally. Replace with enums or pattern constraints.
| Scored | Grade | Overall | Spec posture | Rubric |
|---|---|---|---|---|
| 2026-09-22 | D | 54 | 2026-07-28+ | v2 |
The top trending cryptocurrencies right now, ranked by search interest. Price: $0.001 per call.
A DeFi protocol's current total value locked (TVL), broken out by chain, plus market cap. Data via DefiLlama. Price: $0.003 per call.
Current gas price and EIP-1559 fee estimate for Base, Ethereum, Polygon, Arbitrum, or Optimism. Price: $0.001 per call.
Full detail for a single Kalshi market by ticker: yes/no prices, volume, status, result. Price: $0.002 per call.
Full detail for a single Polymarket market by slug: prices, volume (24h/1wk/total), liquidity, resolution status. Price: $0.002 per call.
Demo of page-level (not just API-level) x402 protection. Returns a short confirmation message. Price: $0.001 per call.
Trend score, momentum, and related trends for a topic. Two tiers: standard ($0.001) returns a basic score, premium ($0.005) returns the full breakdown including related trends.
Native token balance for a wallet address, plus an optional specific ERC-20 token balance, across Base, Ethereum, Polygon, Arbitrum, or Optimism. Price: $0.002 per call.
Live current weather conditions for any city (temperature, conditions, humidity, wind), sourced from Open-Meteo. Price: $0.001 per call.
Minimal heartbeat/ping endpoint, billed via a batch-settlement payment channel so it's cheap to call repeatedly in one session. Price: $0.001 per call.
Ranks blockchains by total DeFi value locked across all protocols. Price: $0.002 per call.
Search or list open Kalshi prediction markets (regulated US event contracts) — title, yes/no bid-ask, volume, close time. Price: $0.003 per call.
Search or list active Polymarket prediction markets, ranked by 24h volume — question, outcomes, prices, volume, liquidity, end date. Price: $0.003 per call.
Real-time web search — ranked results with title, URL, published date, author, and relevance score for a query. Price: $0.003 per call.
Numeric parameters (limit, numResults) lack explicit minValue/maxValue constraints in parameter definitions. E.g., search_polymarket_markets::limit says '1-50 (default 10)' in description only, not in schema constraints.
No error handling patterns visible. Tools do not document recovery paths (e.g., 'If protocol slug not found, call list_protocols() to discover valid slugs'). Agents cannot self-correct.
Tools with list/pagination (search_polymarket_markets, search_kalshi_markets, find_prediction_market_divergence) do not document offset/cursor handling or total count. Agents cannot determine if results are complete.
Tool security scope not declared. No indication of what permissions or rate limits apply. Pattern requires each tool to declare required scopes for audit and least-privilege configuration.