Bitview

CPFP info

get_cpfp

Read-onlyIdempotent

Returns ancestors and descendants for a CPFP (Child Pays For Parent) transaction, including the effective fee rate of the package. A mempool transaction answers its live package; a confirmed one its package among its block's transactions; an unknown transaction, or a confirmed one without relatives in its block, {"ancestors":[]}.

Mempool.space docs

REST operation: GET /api/v1/cpfp/{txid}.

Input Schema

Name	Required	Description	Default
`txid`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed14 schema fields changedOct 30, 2026

changedInput schema / $defs / Txid / description

Previous value: -"Transaction ID (hash)"New value: +"A transaction ID: its hash."

addedInput schema / $defs / Txid / pattern
```
Added value: +"^[0-9a-f]{64}$"
```

addedOutput schema / $defs / ConfirmedCpfp

Added value: +{
+  "properties": {
+    "ancestors": {
+      "items": {
+        "$ref": "#/$defs/CpfpEntry"
+      },
+      "type": "array"
+    },
+    "cluster": {
+      "allOf": [
+        {
+          "$ref": "#/$defs/CpfpCluster"
+        }
+      ]
+    },
+    "descendants": {
+      "items": {
+        "$ref": "#/$defs/CpfpEntry"
+      },
+      "type": "array"
+    },
+    "effectiveFeePerVsize": {
+      "allOf": [
+        {
+          "$ref": "#/$defs/FeeRate"
+        }
+      ]
+    }
+  },
+  "required": [
+    "ancestors",
+    "descendants",
+    "effectiveFeePerVsize",
+    "cluster"
+  ],
+  "type": "object"
+}

addedOutput schema / $defs / Cpfp

Added value: +{
+  "anyOf": [
+    {
+      "$ref": "#/$defs/CpfpInfo"
+    },
+    {
+      "$ref": "#/$defs/ConfirmedCpfp"
+    },
+    {
+      "$ref": "#/$defs/EmptyCpfp"
+    }
+  ]
+}

removedOutput schema / $defs / CpfpCluster / properties / chunkIndex / format
```
Removed value: -"uint32"
```
removedOutput schema / $defs / CpfpClusterTxIndex / format
```
Removed value: -"uint32"
```

addedOutput schema / $defs / EmptyCpfp

Added value: +{
+  "properties": {
+    "ancestors": {
+      "maxItems": 0,
+      "type": "array"
+    }
+  },
+  "required": [
+    "ancestors"
+  ],
+  "type": "object"
+}

removedOutput schema / $defs / FeeRate / format
```
Removed value: -"double"
```
removedOutput schema / $defs / Sats / format
```
Removed value: -"uint64"
```
removedOutput schema / $defs / SigOps / format
```
Removed value: -"uint32"
```
addedOutput schema / $defs / Txid / pattern
```
Added value: +"^[0-9a-f]{64}$"
```
removedOutput schema / $defs / VSize / format
```
Removed value: -"uint64"
```
removedOutput schema / $defs / Weight / format
```
Removed value: -"uint32"
```

changedOutput schema / $ref

Previous value: -"#/$defs/CpfpInfo"New value: +"#/$defs/Cpfp"

First observedOct 23, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuine behavioral context beyond them: results are state-dependent on whether the transaction is in the mempool or confirmed in a block, and an unknown or orphaned transaction yields `{"ancestors":[]}` rather than an error. It omits things like whether the empty-package case is distinguishable from a malformed txid, but this is solid added value over the annotations.

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?

Purpose is front-loaded in the first clause, the three state cases are compressed into one dense sentence each, and the docs link plus REST operation trail at the end where they belong. Nothing is padded.

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 an output schema handling return values and annotations handling the safety profile, the description only needs to carry the semantics of the result set, which it does via the mempool/confirmed/unknown cases. For a single-parameter read tool this is sufficient for correct invocation and interpretation.

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 description coverage is reported as 0%, but the shared Txid definition carries a description plus a hex pattern and three examples, so the format is well documented structurally. The prose adds nothing about the txid beyond what the schema shows; the only semantic hint is the implicit point that the same txid returns different packages depending on its confirmation state.

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 names a specific resource (the CPFP package for a transaction) and a specific payload (ancestors, descendants, and effective package fee rate), which is far more precise than the bare name 'get_cpfp'. It does not explicitly route the agent away from the topically adjacent siblings (get_tx, get_tx_outspends, get_fullrbf_replacements), so it falls short of full sibling differentiation.

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 only implied: the state-by-state explanation (mempool, confirmed, unknown) tells the agent what it will get for a given txid but never states when to prefer this tool over get_tx or get_fullrbf_replacements. There are no explicit when-not conditions or prerequisites.

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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