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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds only the cost trait ("Free" — calling it consumes no credits), which is genuinely useful but thin; it says nothing about rate limits or whether a default/env key is used when api_key is omitted.

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 very short sentences, with the core action stated first. The one-word "Free." sentence is abrupt but earns its place by conveying the key cost fact.

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 simple read-only balance check with full annotation coverage this is adequate, but with no output schema the description never indicates what is returned (a count, a quota object, etc.) or how optional api_key omission is handled.

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 the single api_key parameter is fully documented there. The phrase "on an AI Separations API key" vaguely links the resource to that parameter but adds no syntax or fallback details, so the schema does the heavy lifting.

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 a specific verb (Check) and resource (remaining separation credits on an AI Separations API key). It is inherently distinct from buy_credits and get_pricing, but the description never names those siblings or explicitly contrasts with them.

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 only guidance is the word "Free," which implies cost-free invocation but says nothing about when to check the balance versus when to buy credits or estimate costs. No prerequisites or alternatives are given.

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