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

Annotations already cover the read-only, idempotent, open-world, and non-destructive safety profile, so the description is free to add other useful behavioral context. It adds that a key is required for access, that only the 'last' practice trades are returned, and that sell profit is included in the results, which goes beyond what the annotations state.

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 with no filler. The first sentence states the purpose and output content, and the second gives the essential auth prerequisite. It is front-loaded and every sentence earns its place.

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 listing tool with strong annotations, the description is nearly complete: it names the returned data (last practice trades and sell profit) and the auth requirement. It could be more explicit about what 'this mite' refers to or what other fields are returned, but those are minor gaps given the overall simplicity of the tool.

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?

This tool has zero parameters, so the schema has no information for the description to compensate for. The 'needs a key' note is about authentication rather than a tool argument, which is appropriate here.

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 clearly identifies the resource ('practice trades') and conveys that this returns the most recent ones along with the profit from each sell. It lacks an explicit verb like 'list' or 'get', and it does not explicitly distinguish itself from sibling tools such as practice_account, practice_buy, or practice_sell, but the intended meaning is still clear.

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 description provides no guidance on when to use this tool instead of alternatives like practice_buy, practice_sell, or practice_account. The only usage-related note is the authentication requirement ('Needs a key'), which is necessary but does not help an agent choose between this and sibling tools.

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