Crank Protocol

authorize_session_signer

Idempotent

Refuses ALWAYS with BROWSER_CONFIRMATION_REQUIRED.

Minting (or reactivating) a session signer grants NEW signing authority -- a trust grant at least as sensitive as loosening a policy, which is already browser-gated. This tool therefore refuses EVERY call, for EVERY wallet (not only Lane 2), after validating capabilities for early UX. The only mint path is the browser handshake: request_session_signer_authorization (open) -> the wallet OWNER approves in their browser -> poll_session_signer_authorization (bind the stored payload). signer_pubkey is a keypair the USER creates and holds -- ONLY its PUBLIC key ever crosses this surface (hard rule 1); once authorized via the handshake, calls carrying it are trade-only under tx_verify (docs/SESSION_SIGNER_DESIGN.md).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "wallet_address": "<wallet_address>",
      "signer_pubkey": "<signer_pubkey>"
    },
    "name": "authorize_session_signer"
  }
}

Input Schema

Name	Required	Description	Default
`label`	No
`caller_id`	No
`expires_at`	No
`capabilities`	No
`signer_pubkey`	Yes
`wallet_address`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 27, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Beyond the annotations, the description discloses surprising behavior: the tool always refuses, applies to every wallet, validates capabilities only for UX, and never lets anything but the public signer key cross the surface. It also explains the security rationale and the handshake requirement.

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 first sentence front-loads the most critical behavior, and every subsequent sentence adds relevant context: the reason for refusal, the alternative workflow, and the security rule. There is no filler or repeated schema information.

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?

The description is complete enough for an agent to avoid a doomed call and route to the browser handshake. Minor gaps remain around additional parameter details and the exact output/error payload, but the output schema and the always-refusal design reduce the need for more.

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?

The description adds important meaning for signer_pubkey, explaining it is a user-held keypair and only its public key should cross the surface. However, schema description coverage is 0%, and other parameters such as expires_at, capabilities, label, and caller_id are left mostly to inference from their names.

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?

The description opens with an explicit behavioral statement: 'Refuses ALWAYS with BROWSER_CONFIRMATION_REQUIRED.' It clearly defines what the tool does, why it exists, and differentiates it from the actual authorization flow via request_session_signer_authorization and poll_session_signer_authorization.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly tells the agent when not to use this tool by stating every call is refused and names the only valid mint path: the browser handshake sequence. This is strong when-to-use and when-not-to-use guidance with named alternatives.

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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