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

Even though annotations already mark it as non-read-only, the description adds substantial behavioral detail: the fill includes fees, tax, and price impact; the simulation runs against the current block state; accounts start with 1 practice eth; nothing real is spent; and the result indicates whether the buy could be sold straight back. No contradiction with annotations.

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 dense sentences with the core action front-loaded, followed only by behaviorally relevant simulation details and the key prerequisite. Every sentence earns its place with no filler.

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 two-parameter tool with no output schema, the description covers mechanics, pricing realism, account balance, safety, return information, and authentication. Nothing essential is missing for an agent to understand and invoke the tool 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?

Schema description coverage is 100% and already documents the eth format, minimum amount, and token pattern. The tool description adds useful global context but no per-parameter meaning beyond what the schema already provides, so baseline 3 is appropriate.

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 states a specific action ('buys a token') with a precise resource ('with pretend eth at the real price') and clarifies it is a simulation through the same route as a real trade. This clearly distinguishes practice_buy from siblings like practice_sell and prepare_buy.

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 intended context is clear: use it for a paper-trade buy with pretend eth, with no real funds spent. It also supplies a prerequisite (needs a key), but it does not explicitly name alternatives or state when not to use it.

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