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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds operational context: it is free, completes when the guide text returns, causes no purchase or payment, and requires no human decision. This aligns with and enriches the annotation safety profile.

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?

Four sentences, each carrying distinct value: what the guide contains, cost, completion behavior, and routing away from buy_* tools. The key disambiguation is front-loaded before the behavioral note.

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?

For a zero-parameter, read-only informational tool with an output schema, the description fully covers what the tool does, when to use it, and what it cannot do. No missing context would prevent an agent from calling it correctly.

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 takes zero parameters, so the schema describes everything needed. Baseline for 0 params is 4; the description doesn't need to add parameter detail, and it doesn't.

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?

States the exact resource ('the store's front door as text') and the verb ('read') through the name. The description enumerates the guide's contents (menu with prices, x402 payment info, free shelf, house promises) and explicitly disambiguates from purchase endpoints by saying it is 'NOT a purchase or payment endpoint'.

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?

Provides explicit routing: to buy, call a buy_* tool with x402 payment in _meta['x402/payment']; this tool only returns the guide. It also frames the tool as an autonomous store errand for the visiting agent, signaling that no human approval is required.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.