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

Annotations only cover read-only and non-open-world; the description adds that the call validates the key and returns plan and weekly quota, which is real behavioral content, especially with no output schema. It stops short of describing failure modes or quota reset semantics, but it discloses what the agent will learn.

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?

Two tight sentences with zero filler. The core action and its result are front-loaded, followed by the usage rationale.

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 no-parameter, no-output-schema diagnostic tool, the description conveys what it validates and what it returns, which is enough for correct invocation. Minor gaps remain around quota period semantics and error behavior, but nothing blocking.

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 has nothing to explain and the baseline is 4. Nothing in the description is needed to compensate for parameter documentation.

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 specific verbs and resources: confirm API key validity and report current plan plus weekly backtest quota. No sibling tool does this, so an agent can distinguish it immediately from the strategy/portfolio/backtest tools.

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?

Explicitly recommends calling it first in a conversation so later failures aren't a surprise, which is clear triggering context. It doesn't state when not to call it or name a comparable alternative, but none of the siblings overlap with this function.

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