Ethereum remains the largest smart contract ecosystem by total value locked, active developers, and deployed applications. For teams building on top of it, the API layer determines how quickly they can ship, how reliably their applications perform, and how much infrastructure they end up managing themselves.
That decision has become more complex in 2026. AI agents are entering the Ethereum ecosystem in growing numbers, handling tasks that range from autonomous portfolio rebalancing to DeFi yield optimization. These agents need structured, real-time data delivered through interfaces that software can consume without human intervention. Not every Ethereum API is built for that.
This guide covers five Ethereum API providers, each designed for a different part of the development stack. For a broader comparison of crypto data providers across all chains, the best crypto apis guide covers additional options worth evaluating.
Why Ethereum APIs Matter for AI Agents
AI agents operating in crypto need more than raw RPC access. An autonomous portfolio manager, for example, needs token balances, historical price data, DeFi positions, and transaction histories delivered in a structured format it can parse and act on without custom data pipelines. A trading agent needs real-time pricing across multiple exchanges. A compliance agent needs wallet activity logs with enriched metadata.
The following types of AI agents are increasingly relying on Ethereum API infrastructure in 2026:
- Portfolio rebalancing agents continuously monitor wallet holdings across chains and protocols, compare allocations against target weights, and execute trades or swaps to maintain balance. They require multi-chain wallet data, live pricing, and DeFi position tracking.
- DeFi yield optimization agents scan lending protocols, liquidity pools, and staking programs across Ethereum and its Layer 2 networks to identify optimal yield opportunities. They need protocol-level data covering APYs, TVL, and position metadata.
- Trading and arbitrage agents operate across centralized and decentralized exchanges, looking for price discrepancies and executing trades in milliseconds. They depend on aggregated market data with low latency.
- Research and sentiment agents ingest market data alongside news feeds and on-chain activity to generate reports, flag anomalies, or adjust risk parameters in real time.
- Multi-chain wallet monitoring agents track activity across Ethereum, its L2 rollups, and other EVM chains, alerting users to inbound transfers, suspicious transactions, or significant balance changes.
- Tax and compliance agents parse transaction histories, calculate cost basis, and generate regulatory reports. They need enriched transaction data with USD-denominated values and token metadata.
- Conversational crypto assistants respond to natural language queries about portfolio performance, token prices, or market conditions. These agents need a data interface that LLMs can call directly.
Each of these agent types has different data requirements, but they share a common need: clean, structured, and reliable API access to Ethereum data. The providers below address different segments of that stack.
1. CoinStats Ethereum API
CoinStats Ethereum API is built for developers and AI agents that need aggregated, application-ready Ethereum data without assembling multiple providers. Rather than exposing raw RPC endpoints, CoinStats API returns pre-structured wallet balances, transaction histories, DeFi positions, and market data through a unified REST interface. This makes it the most practical option for the majority of crypto development use cases where the goal is building applications on top of Ethereum data rather than interacting with the chain at the node level.
Ethereum and EVM Coverage
The API covers Ethereum mainnet alongside all major EVM-compatible networks through a single integration. Supported chains include Polygon, Arbitrum, Optimism, Avalanche, Base, and BSC, among others. A single API call using the multi-chain balance endpoint returns token holdings across all supported EVM chains simultaneously, so developers do not need separate integrations for each network.
For Ethereum specifically, the API returns native ETH and all ERC-20 token balances with USD pricing, 24-hour price changes, token metadata, and ranking data already enriched in the response. Transaction history endpoints deliver fully parsed records with gas fee tracking included. DeFi position tracking covers staking, lending, and liquidity pool holdings across 10,000+ protocols automatically, without requiring developers to integrate each protocol individually.
Broader Data Surface
Beyond wallet data, the CoinStats API provides market data for 100,000+ cryptocurrencies aggregated from 200+ exchanges (including Binance, Coinbase, and Hyperliquid), covering 120+ blockchains in total. A news and sentiment feed aggregated from crypto media sources adds another data dimension for research-oriented applications. Wallet support extends to Solana, Bitcoin (including xpub/ypub/zpub formats), and additional non-EVM chains, all accessible through the same API key and consistent response schema.
MCP Server for AI Agent Integration
CoinStats API provides a Model Context Protocol (MCP) Server alongside its REST API, which is the feature most relevant to the AI agent use case. The MCP Server exposes market data and wallet endpoints as callable tools for AI assistants and developer environments, including Claude, Cursor, and VS Code. This means AI agents can query Ethereum wallet balances, token prices, or DeFi positions using natural language through an MCP-compatible interface, without writing custom API integration code.
For teams building any of the seven agent types described above, particularly portfolio rebalancing agents, conversational crypto assistants, and research agents, the MCP Server removes the data integration layer entirely. The agent describes what it needs, and the MCP Server translates that into the appropriate API call.
Pricing and Access
CoinStats API uses a credit-based pricing model with a free tier available at signup. Credit costs vary by endpoint complexity: a single-chain Ethereum balance query costs 40 credits, while a multi-chain query across all EVM networks costs 400 credits. Developers can monitor usage in real time through the OpenAPI dashboard. The platform serves 1M monthly users, and its documentation is hosted at coinstats.app/api-docs/.
Best for: Most crypto development use cases. Developers and AI agents that need unified Ethereum and multi-chain data aggregation, portfolio tracking, DeFi position monitoring, and MCP-based AI integration through a single provider.
2. Chainstack
Chainstack is a multi-chain RPC and node infrastructure provider that gives developers direct access to Ethereum’s JSON-RPC interface. Where CoinStats API delivers aggregated, application-ready data, Chainstack provides the raw blockchain access layer: full and archive nodes, debug and trace methods, and WebSocket connections for real-time event streaming.
The platform supports 70+ chains and routes requests through a globally distributed infrastructure with 99.99% measured uptime. Ethereum developers get access to both mainnet and testnets (Sepolia, Hoodi) through authenticated endpoints with configurable rate limits. Chainstack’s Trader Node product offers low-latency mempool access for teams building MEV-aware applications or high-frequency trading infrastructure.
Pricing follows a request-unit model with a free tier offering 3 million request units per month at up to 25 requests per second. The Growth plan provides 20 million request units and 250 RPS for production workloads. Enterprise plans support custom RPS configurations and dedicated infrastructure. Chainstack holds SOC 2 Type II certification, which is relevant for teams operating under compliance requirements.
Best for: Developers building dApps, trading bots, or backend infrastructure that needs direct Ethereum node access with enterprise-grade reliability and compliance controls.
3. Ankr
Ankr operates a decentralized physical infrastructure network (DePIN) that provides RPC access and pre-indexed blockchain data across 70+ chains. On Ethereum, Ankr offers both standard Node API access (JSON-RPC over HTTPS and WSS) and an Advanced API layer with pre-indexed, cached methods for faster queries.
The Advanced API is where Ankr differentiates itself from pure RPC providers. Methods like ankr_getAccountBalance and ankr_getTokenPrice return enriched data across multiple chains in a single request, reducing the number of calls needed to assemble a complete picture of a wallet’s holdings. NFT-specific endpoints cover ownership lookups, metadata retrieval, and transfer histories. Ankr supports multi-chain queries natively, so a single call can return token balances from Ethereum, Polygon, Arbitrum, and other EVM chains simultaneously.
Pricing uses an API credit system pegged to USD, where different methods consume different credit amounts. A Freemium tier includes 200 million monthly API credits using public rate limits. The Premium tier unlocks private endpoints, debug and trace methods, higher rate limits, and WebSocket access. Ankr’s DePIN infrastructure spans 30+ global regions with an average response time of 56 milliseconds.
Best for: Developers who need a combination of standard RPC access and pre-indexed multi-chain data queries, with decentralized infrastructure and pay-per-method pricing.
4. Etherscan API
Etherscan is the standard block explorer for Ethereum, and its API provides programmatic access to the same indexed data the explorer displays. For developers who need verified contract ABIs, internal transaction traces, gas price estimates, or token transfer logs, Etherscan remains the primary source.
The API covers account balance and transaction lookups, ERC-20/ERC-721/ERC-1155 token transfer events, contract source code and verification status, gas tracker data, and block/uncle information. The event log endpoints are particularly useful for applications that need to filter and retrieve specific on-chain events without running their own indexer.
Etherscan operates separate API instances for Ethereum mainnet and its major L2/sidechain counterparts (Polygonscan, Arbiscan, BaseScan, and others), though each requires its own API key and has a slightly different endpoint structure. The free tier allows up to 5 calls per second, which is sufficient for development and low-traffic applications. Pro plans offer higher rate limits and additional endpoints.
A key limitation is that Etherscan is read-only and Ethereum-specific. It does not provide market data, pricing, portfolio aggregation, or DeFi position tracking. For AI agents, it serves best as a complementary data source for contract verification, gas estimation, and raw transaction lookups rather than as a primary data layer.
Best for: Developers who need verified contract data, event logs, gas estimates, and granular Ethereum transaction details for analytics, auditing, or compliance tools.
5. The Graph
The Graph is a decentralized indexing protocol that allows developers to build and query custom APIs (called subgraphs) for Ethereum smart contract data. Rather than pulling data through pre-built endpoints, developers define a schema and mapping logic that tells The Graph which contracts and events to index. The indexed data is then served through GraphQL queries.
As of 2026, The Graph indexes data across 40+ chains, with Ethereum accounting for the majority of deployed subgraphs. Over 1,100 projects use the protocol, including major DeFi applications like Uniswap, Aave, and Balancer. The Hosted Service has been fully deprecated; all subgraphs now run on the decentralized network, where indexers stake GRT tokens and are economically incentivized to serve accurate data.
The Graph is most valuable for teams that need custom, event-driven data models. A developer building a DEX analytics dashboard, for example, can define a subgraph that indexes every swap event on a specific contract and serves aggregated volume and price data through a GraphQL endpoint. This level of customization is not available through general-purpose REST APIs.
The trade-off is complexity. Building and maintaining subgraphs requires writing AssemblyScript mapping code and managing deployment through The Graph’s tooling. Query costs on the decentralized network are paid in GRT tokens, with pricing around $1.50 to $2 per 100,000 queries. A free tier of 100,000 queries per month is available through the Subgraph Studio.
Best for: Developers who need custom-indexed Ethereum smart contract data served through GraphQL, particularly for DeFi analytics, NFT marketplaces, and protocol dashboards.
Choosing the Right Ethereum API
The five providers above serve fundamentally different roles in the Ethereum development stack, and the right choice depends on what you are building and how your application consumes data.
If your project is a portfolio tracker, a multi-chain dashboard, a financial reporting tool, or an AI agent that needs structured crypto data, CoinStats Ethereum API covers the broadest surface through a single integration. The MCP Server adds a layer that none of the other providers currently offer: the ability for AI agents and LLM-powered tools to query Ethereum data through conversational interfaces without custom integration code.
If you need direct Ethereum node access for dApp backends, smart contract interaction, or MEV-aware trading, Chainstack and Ankr provide the infrastructure layer. Chainstack offers the most predictable pricing and strongest compliance certifications, while Ankr adds pre-indexed multi-chain query methods on top of standard RPC.
For contract verification, gas estimation, and granular transaction data, Etherscan remains the standard reference source for Ethereum-specific lookups.
And for teams that need deeply customized, event-driven data models from specific smart contracts, The Graph provides indexing infrastructure that no pre-built API can replicate.
Many production applications combine two or more of these providers: CoinStats API for aggregated data and AI integration, a node provider like Chainstack for direct chain interaction, and The Graph for custom-indexed protocol data. Starting with a free tier across any of these providers and scaling into paid plans once usage patterns are clear is the most effective way to evaluate.
