AgentIndex x402

Gas Price

gas_price

Read-onlyIdempotent

Read the live gas price, EIP-1559 base fee and estimated native-transfer cost on Base, Ethereum, Polygon, Arbitrum or Optimism. No RPC key or account. Try GET /gas-price/sample.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`network`	No	EVM network to read; defaults to Base.	base

Output Schema

TableJSON Schema

Name	Required	Description	Default
`network`	Yes
`base_fee`	No
`gas_price`	Yes
`block_number`	Yes
`x402_receipt`	No
`native_transfer_estimate`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 27, 2026

addedInput schema / properties / network / description

Added value: +"EVM network to read; defaults to Base."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "base_fee": {
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "block_number": {
+      "type": "integer"
+    },
+    "gas_price": {
+      "type": "object"
+    },
+    "native_transfer_estimate": {
+      "type": "object"
+    },
+    "network": {
+      "type": "object"
+    },
+    "x402_receipt": {
+      "type": "object"
+    }
+  },
+  "required": [
+    "network",
+    "block_number",
+    "gas_price",
+    "native_transfer_estimate"
+  ],
+  "type": "object"
+}

AddedSep 20, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so the safety profile is covered. The description adds genuinely new context beyond the annotations: no RPC key or account is required, and the reading is 'live' across five named chains. It does not discuss rate limits, freshness latency, or caching behavior, so it stops short of a 5.

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?

Two tightly written sentences with the core capability front-loaded and no filler. The trailing 'Try GET /gas-price/sample' is a useful invocation hint but is slightly cryptic out of context, keeping this just below a perfect score.

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?

An output schema exists, so return-value explanation is unnecessary, and the description covers the networks, the absence of auth requirements, and the three data points returned. It is complete enough to invoke correctly, though it omits units/currency conventions for the cost estimate and any note about update frequency.

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% and the single parameter defaults to Base, so the baseline is 3. The description adds meaning the schema lacks: it enumerates the valid network values (Base, Ethereum, Polygon, Arbitrum, Optimism) even though the schema declares no enum for that field, which is real compensating value.

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 verb and resource ('Read the live gas price, EIP-1559 base fee and estimated native-transfer cost') and enumerates the five supported networks. It is clearly distinguishable from siblings like wallet_balance, can_pay, and crypto, which concern balances or payment decisions rather than fee data.

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

Usage Guidelines3/5

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

Usage is implied by the purpose (call this when you need fee data), and 'No RPC key or account' removes a common prerequisite question. However, there is no explicit when-to-use statement, no exclusions, and no routing to a sibling such as can_pay when the question is really about affordability.

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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