locker_capabilitiesFree. Returns the machine-readable contract — identity model, signing statements, prices, limits, custody commitments (deletion rules, 30-day sunset), x402 payment flow, and error codes. Call this first.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses that the tool is free, returns a machine-readable contract, and details what is included (deletion rules, 30-day sunset, x402 payment flow, error codes). It stops short of explicitly stating that it has no side effects or requires no authentication, but the informational nature is strongly implied.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two sentences, front-loaded with 'Free' and 'Returns', and every phrase adds value. The enumerations are compact yet comprehensive, and the instruction 'Call this first' is actionable. No filler or redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given zero parameters, no output schema, and no annotations, the description covers all critical aspects: cost, return contents, and usage order. The enumeration of contract components is sufficiently detailed for an agent to know what to expect, and the 'call first' guidance provides the needed context within the sibling tool suite.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool has zero parameters, so the baseline is 4. The description adds no parameter-specific details, but none are needed. The empty schema already communicates that no arguments are required.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses a specific verb ('Returns') and clearly identifies the resource (the machine-readable contract), then enumerates its key contents (identity model, prices, limits, custody commitments, x402 payment flow, error codes). This distinguishes it from sibling tools like locker_send or locker_status, which perform specific actions rather than exposing the full contract.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The phrase 'Call this first' gives explicit sequencing guidance, indicating that this tool should be used before others to understand the contract. It does not explicitly state when not to use it or name alternatives, but the context makes its role as the discovery entry point clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool has a clearly distinct purpose: send, read, ack, count, register_key, directory, nonce, capabilities, credit, checkpoint, and status cover different operations without overlap. Even similar-sounding tools like count and read are cleanly separated by scope (message count vs. message content).
All tool names follow a uniform pattern with the 'locker_' prefix and lowercase snake_case. While some postfixes are nouns (capabilities, directory, status) and others verbs (send, read, ack), the style is consistent and predictable, matching the server's domain.
11 tools is well-scoped for a messaging/storage server: each tool earns its place covering setup, messaging, payment, and account management without redundancy or bloat.
The tool surface provides complete lifecycle coverage for the mailbox system: key registration, message sending/reading/acknowledging, directory lookup, nonce generation, payment via credit, persistent checkpoint storage, and status monitoring. No obvious dead ends or missing operations for the stated purpose.