QuickBuild token-saver tools + x402

Crypto prices (ticker, id or contract)

crypto_price

Read-onlyIdempotent

[PAID $0.001 USDC per call via x402 on Base; errors are free] Live crypto prices for up to 25 coins per call: pass tickers in symbols (BTC,ETH,SOL,AERO,...; common tickers built in, others resolved by CoinGecko search to the largest coin with that ticker), CoinGecko ids, or one token address + chain (base default; ethereum, arbitrum, optimism, polygon, bsc, avalanche, solana). Returns price, market cap, 24h volume and 24h % change in each vs currency (usd default; up to 5, e.g. usd,eur,btc) plus last-updated time. Each USD price is cross-checked against Coinbase spot: sources {coingecko, coinbase} and deviationPct per coin, maxDeviationPct overall. Data: CoinGecko public API, cached 15 s; falls back to Coinbase spot rates (price only) if CoinGecko is unavailable. All params optional: with none it returns BTC and ETH in USD. Unknown coins = 404, invalid input = 400, never charged.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "crypto_price"
  }
}

Input Schema

Name	Required	Description
`vs`	No	Comma-separated quote currencies (max 5), e.g. usd,eur,btc. Default usd.
`ids`	No	Comma-separated CoinGecko coin ids, e.g. bitcoin,aerodrome-finance (optional).
`chain`	No	Chain of `address` (default base).
`address`	No	Optional token contract address; returns that token price (overrides symbols/ids).
`symbols`	No	Comma-separated tickers, e.g. BTC,ETH,SOL (max 25). Optional: defaults to BTC,ETH.

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 21, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already cover read-only/idempotent, but the description adds substantive traits: pay-per-call pricing ($0.001 USDC via x402 on Base, errors free), 15 s cache, Coinbase cross-check with deviationPct, fallback data source, and concrete error codes (404 unknown coin, 400 invalid input, never charged). That is well beyond what the annotations disclose.

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

Conciseness4/5

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

Dense but front-loaded, leading with price/cost before capabilities. Nearly every clause carries information, though the single-paragraph packing of pricing, inputs, outputs, cross-check and error codes is close to overstuffed and could be split for scanability.

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

Completeness5/5

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

With no output schema, the description fully compensates by enumerating returned fields (price, market cap, 24h volume, 24h % change, sources, deviationPct, maxDeviationPct, last-updated), defaults, limits and error behavior. An agent has everything needed to call it and interpret the response.

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

Parameters4/5

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

Schema coverage is 100%, so a 3 is the baseline, but the description adds genuine meaning the schema lacks: how unknown tickers are resolved (CoinGecko search to the largest coin with that ticker), the built-in common tickers, the max-5 quote currency cap with examples, and the chain list. It does not distinguish which chains support address lookups vs which don't.

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?

States a specific verb and resource ('Live crypto prices') plus the three accepted identifier forms (tickers, CoinGecko ids, address+chain). It distinguishes itself from siblings like fx_rate (fiat) and base_token_info/sol_token (single-chain token metadata) by making clear this is cross-chain price lookup with multi-currency quotes.

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?

Gives explicit precedence among input modes ('address overrides symbols/ids'), the default behavior with no params (BTC and ETH in USD), and the fallback condition (CoinGecko unavailable → Coinbase spot). It doesn't explicitly say when to prefer this over fx_rate or the chain-specific token tools, but the context is otherwise unambiguous.

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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