SiteCheck Crypto & Finance

Polygon PoS checkpoints from the Heimdall API: the latest K

crypto_polygon_pos_checkpoints

Read-only

Polygon PoS checkpoints from the Heimdall API: the latest K checkpoints (1 to 10) with their Bor block range, timestamp and proposer, plus the average spacing in blocks and seconds. Checkpoints are the Ethereum-anchored root commitments. State-sync logs are not included. Price: $0.002 in USDC per successful call, paid with x402 (Base, Solana or Arc); failed calls are not 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_polygon_pos_checkpoints"
  }
}

Input Schema

Name	Required	Description	Default
`count`	No	How many latest checkpoints, 1 to 10 (default 3)

Output Schema

Name	Required	Description	Default
`count`	No
`source`	No
`checkedAt`	No
`checkpoints`	No
`avgBlocksBetween`	No
`avgSecondsBetween`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 23, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already cover read-only and open-world status, but the description adds what annotations cannot: the paid x402 pricing model ($0.002 USDC per successful call), the accepted payment chains, and that failed calls are not charged. That is exactly the kind of cost/side-effect context an agent needs before committing to a call; it does not explain rate limits or data freshness/latency.

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?

One front-loaded paragraph: what it returns first, exclusions next, cost last. Every clause carries information — field list, scope bound, exclusion, pricing — with no 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?

With one optional parameter and an output schema, the description needn't explain return structure, and it covers source (Heimdall), content, exclusions, and cost. The remaining gap is freshness/recency semantics for 'latest' and failure behavior, which a caller might still want.

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 coverage is 100% and the single 'count' parameter already documents 'How many latest checkpoints, 1 to 10 (default 3)'. The description's '1 to 10' simply restates that, adding no new format, default, or edge-case meaning.

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?

Names a specific verb and resource ('Polygon PoS checkpoints from the Heimdall API'), specifies the scope (latest K, 1–10) and enumerates returned fields (Bor block range, timestamp, proposer, average spacing). It also explicitly excludes state-sync logs, which separates it from the neighbouring Heimdall/Bor data tools.

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?

The 'State-sync logs are not included' line tells the agent what this tool will not answer, which implies where to look elsewhere, and the count range frames the call. It stops short of naming an alternative sibling or stating prerequisites, so it is clear context rather than full when/when-not routing.

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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