Verify a contract's SHA-256 hash to confirm document integrity. Checks whether the provided hash matches a contract stored on Ambr. Returns verification status, contract metadata, and Reader Portal URL if found. Args: - hash (string, required): SHA-256 hash (64-character hex string) Returns: - ve...
Part of the Ambr server.
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AI agents call ambr_verify_hash to retrieve information from Ambr without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though ambr_verify_hash only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"ambr_verify_hash": {}
}
}See the full Ambr policy for all 6 tools.
These attack patterns abuse exactly the kind of access ambr_verify_hash gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Verify a contract's SHA-256 hash to confirm document integrity. Checks whether the provided hash matches a contract stored on Ambr. Returns verification status, contract metadata, and Reader Portal URL if found. Args: - hash (string, required): SHA-256 hash (64-character hex string) Returns: - verified: boolean - contract_id: string (if found) - status: string (if found) - reader_url: string (if found) Legibility: verification is the point at which legibility becomes provable — matching hash means the prose a human reads and the JSON a machine parses are the same document that was originally signed.. It is categorised as a Read tool in the Ambr MCP Server, which means it retrieves data without modifying state.
Register the Ambr MCP server in PolicyLayer and add a rule for ambr_verify_hash: 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 Ambr. Nothing to install.
ambr_verify_hash is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the ambr_verify_hash 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.
Set action: deny in the PolicyLayer policy for ambr_verify_hash. 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.
ambr_verify_hash is provided by the Ambr MCP server (https://getamber.dev/api/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 6 Ambr tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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