Agent Data API

base_nft_metadata

Metadata for an ERC-721 or ERC-1155 token on Base: collection name, current owner (ERC-721), token URI, and the metadata JSON fetched and decoded from IPFS, Arweave, HTTPS or an inline data URI, with a browser-loadable image URL. Costs $0.008 USDC on Base via x402.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "contract": "<contract>",
      "tokenId": "<tokenId>"
    },
    "name": "base_nft_metadata"
  }
}

Input Schema

Name	Required	Description	Default
`tokenId`	Yes	Token id as a decimal string
`contract`	Yes	NFT collection contract on Base

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 24, 2026

TDQS

A4.2/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full behavioral burden and does disclose important context: the tool costs $0.008 USDC on Base via x402 and returns decoded metadata plus a browser-loadable image URL. It does not spell out error behavior, read-only semantics, or payment mechanics, so it falls short of a full behavioral profile.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded: it states what the tool returns first, then adds the cost note. Both sentences carry useful information without filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description appropriately lists the important return values and metadata sources. It also discloses cost, but could be more complete by describing payment requirements or error cases for missing metadata.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the contract and tokenId parameters are already fully documented in the schema. The description does not add parameter-level syntax or constraints beyond what the schema provides, making the baseline 3 appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource (NFT metadata), chain (Base), and token standards (ERC-721/ERC-1155), and lists the returned fields. This clearly distinguishes it from sibling chain-specific NFT metadata tools such as eth_nft_metadata, arbitrum_nft_metadata, and polygon_nft_metadata.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives clear usage context: this is for NFT metadata on Base, for ERC-721 or ERC-1155 tokens. It does not explicitly name sibling alternatives or state when not to use it, but the chain-specific framing is sufficient for an agent to route correctly.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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