compose_cancel · 21e14 MCP: Risk & Policy

WHAT IT DOES

What compose_cancel does on 21e14

AI agents invoke compose_cancel to trigger actions in 21e14. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

Parameter	Type	Required	Description
`address`	string	Yes	Source Bitcoin address (must be order creator)
`inputs_set`	string	—	Comma-separated UTXOs to use as inputs (txid:vout)
`offer_hash`	string	Yes	Transaction hash of the order to cancel
`sat_per_vbyte`	number	—	Fee rate in satoshis per virtual byte (e.g. 1, 5.5, 0.15). Check get_fee_estimate for current market rates.

Parameters from the server's own tool schema.

THE RISK

High Risk

Why compose_cancel needs a policy

This tool composes a blockchain transaction to cancel an open DEX order on the Counterparty/Bitcoin protocol. While 'cancel' could seem destructive, composing a transaction is an Execute-level action — it constructs and prepares an on-chain operation. The actual irreversible effect (broadcasting) would occur via a separate broadcast step.

From the tool's definition Compose a transaction to cancel an open DEX order

Documented attack patterns abuse exactly the kind of access compose_cancel gives an agent:

POLICY

How to control compose_cancel

PolicyLayer is an MCP gateway — it sits between your AI agents and 21e14, and nothing reaches the server without passing your rules. This is the rule we recommend for compose_cancel:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "compose_cancel": {
      "limits": [
        {
          "counter": "compose_cancel_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

compose_cancel stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register 21e14 — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

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EXPLORE

Related tools and policies

More 21e14 tools

Financial compose_btcpay Compose a BTC payment for a matched DEX order. Used to complete BTC trades on the DEX. Financial compose_dispense Compose a transaction to buy from a dispenser by sending BTC to it Financial compose_dividend Compose a transaction to distribute dividends to all holders of an asset Financial compose_fairmint Compose a transaction to mint tokens from an active fair minter Financial compose_sweep Compose a transaction to sweep all assets and/or BTC from one address to another Financial compose_issuance Compose a transaction to issue (create) a new Counterparty asset, or update an existing on Financial compose_mpma Compose a multi-party multi-asset send transaction. Sends multiple assets to multiple dest Financial compose_order Compose a DEX order to trade Counterparty assets. IMPORTANT: give_quantity and get_quantit

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Go deeper

High-risk tools in 21e14 → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about compose_cancel

What does the compose_cancel tool do? +

Compose a transaction to cancel an open DEX order. It is categorised as a Execute tool in the 21e14 MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does compose_cancel accept? +

compose_cancel accepts 4 parameters: address, inputs_set, offer_hash, sat_per_vbyte. Required: address, offer_hash. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on compose_cancel? +

Register the 21e14 MCP server in PolicyLayer and add a rule for compose_cancel: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches 21e14. Nothing to install.

What risk level is compose_cancel? +

compose_cancel is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit compose_cancel? +

Yes. Add a rate_limit block to the compose_cancel rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block compose_cancel completely? +

Set action: deny in the PolicyLayer policy for compose_cancel. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides compose_cancel? +

compose_cancel is provided by the 21e14 MCP server (@21e14/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every 21e14 tool call.

Start from 21e14, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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