Blockstream Info

Block

block

Read-onlyIdempotent

Block by 64-char hex hash or by height.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "hash_or_height": "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"
    },
    "name": "block"
  }
}

Input Schema

Name	Required	Description	Default
`network`	No
`hash_or_height`	Yes	Block hash (hex) or numeric height as string.

Output Schema

Name	Required	Description
`id`	No	Block hash
`bits`	No	Difficulty bits
`size`	No	Block size in bytes
`nonce`	No	Block nonce
`height`	No	Block height
`weight`	No	Block weight
`version`	No	Block version
`tx_count`	No	Transaction count
`timestamp`	No	Block timestamp (unix)
`difficulty`	No	Difficulty
`mediantime`	No	Median block time
`merkle_root`	No	Merkle root hash
`previousblockhash`	No	Previous block hash

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 27, 2026
- changedOutput schema / properties / previousblockhash / type
```
Previous value: -"string"New value: +[
+  "string",
+  "null"
+]
```

Changed2 schema fields changedMay 27, 2026

addedInput schema / examples

Added value: +[
+  {
+    "hash_or_height": "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"
+  },
+  {
+    "hash_or_height": "840000",
+    "network": "mainnet"
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "bits": {
+      "description": "Difficulty bits",
+      "type": "number"
+    },
+    "difficulty": {
+      "description": "Difficulty",
+      "type": "number"
+    },
+    "height": {
+      "description": "Block height",
+      "type": "number"
+    },
+    "id": {
+      "description": "Block hash",
+      "type": "string"
+    },
+    "mediantime": {
+      "description": "Median block time",
+      "type": "number"
+    },
+    "merkle_root": {
+      "description": "Merkle root hash",
+      "type": "string"
+    },
+    "nonce": {
+      "description": "Block nonce",
+      "type": "number"
+    },
+    "previousblockhash": {
+      "description": "Previous block hash",
+      "type": "string"
+    },
+    "size": {
+      "description": "Block size in bytes",
+      "type": "number"
+    },
+    "timestamp": {
+      "description": "Block timestamp (unix)",
+      "type": "number"
+    },
+    "tx_count": {
+      "description": "Transaction count",
+      "type": "number"
+    },
+    "version": {
+      "description": "Block version",
+      "type": "number"
+    },
+    "weight": {
+      "description": "Block weight",
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

First observedMay 13, 2026

TDQS

B3.3/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, covering safety and side-effect behavior. The description adds the specific hash format (64-char hex) and the height alternative, which is useful but not extensive. It does not disclose error behavior, network handling, or response format beyond what the output schema already provides.

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 a single concise sentence with no filler. It front-loads the core action and input alternatives efficiently. Every word adds value.

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

Completeness3/5

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

The tool has an output schema, so return values do not need explanation. However, the 'network' parameter is undocumented in both schema and description, leaving agents uncertain about its purpose or default. The description is sufficient for a simple read operation but not fully complete given the undocumented parameter.

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

Parameters2/5

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

The schema covers 50% of parameters with descriptions: 'hash_or_height' has a description, but 'network' does not. The description mentions 'height' and '64-char hex hash,' which partially overlaps with the schema. It does not explain the 'network' parameter or its default behavior, so it fails to compensate for the 50% schema coverage gap.

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

Purpose4/5

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

The description states a clear verb and resource: 'Block' by '64-char hex hash or by height.' This is specific and unambiguous. It does not explicitly differentiate from siblings like 'transaction' or 'mempool,' but the intent is obvious. Slight deduction for not mentioning the context (blockchain) or naming alternatives.

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?

The description gives no explicit guidance on when to use this tool versus alternatives. There are many siblings (e.g., 'transaction', 'mempool'), but the purpose is clear enough that an agent can infer when to call it. However, it does not state any exclusions or prerequisites (e.g., network default, required hash format).

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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