Spot USD price for a token/coin. Provide 'id' (CoinGecko id, e.g. 'ethereum', 'usd-coin') or 'contract'+'chain'. x402 paid: $0.004 USDC on Base per call.
| Name | Required | Description | Default |
|---|---|---|---|
| id | No | CoinGecko coin id, e.g. 'ethereum', 'usd-coin' | |
| chain | No | Chain: ethereum, base, arbitrum, polygon, optimism | ethereum |
| contract | No | Token contract (alternative to id) |
Changes observed during successful MCP inspections.
Input schema / $schemaRemoved value: -"http://json-schema.org/draft-07/schema#"Input schema / additionalPropertiesRemoved value: -falseInput schema / properties / chainAdded value: +{
+ "default": "ethereum",
+ "description": "Chain: ethereum, base, arbitrum, polygon, optimism",
+ "type": "string"
+}Input schema / properties / contract / descriptionPrevious value: -"ERC-20 contract address (0x...)"New value: +"Token contract (alternative to id)"Input schema / properties / contract / patternAdded value: +"^0x[0-9a-fA-F]{40}$"Input schema / properties / id / descriptionPrevious value: -"CoinGecko coin id (e.g. 'ethereum')"New value: +"CoinGecko coin id, e.g. 'ethereum', 'usd-coin'"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does disclose a meaningful behavioral trait: x402 paid at $0.004 USDC on Base per call, which is critical for an agent to know before invoking. It also clarifies the price is 'spot' (not historical). It stops short of describing error/fallback behavior when a token isn't found.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, no filler, and the core purpose plus payment cost are front-loaded. Every clause earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple read-style price tool with no annotations and no output schema, the description covers purpose, inputs, and cost. It could add a note on what the response contains (e.g., currency/price fields) to fully close the loop, but it is largely complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so baseline is 3, but the description adds genuine value by stating the either/or relationship between 'id' and 'contract'+'chain' that the schema alone does not make explicit. It also supplies concrete id examples ('ethereum', 'usd-coin').
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb+resource: spot USD price for a token/coin. An agent can distinguish this single-token price lookup from siblings like cortex_prices or cortex_aggregate_prices, though the description doesn't explicitly name those alternatives to sharpen the distinction.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Explains the two input paths (id OR contract+chain), which functions as usage guidance, but gives no explicit when-to-use/when-not guidance relative to the price-related siblings. Usage is implied rather than stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.