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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description goes beyond that by disclosing required auth scopes (user:read, billing:read) and specifying the returned facets (balance, burn, runway), which annotations do not carry. It stops short of units, freshness, or rate-limit behavior.

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: the resource and its content first, the prerequisite second. No filler, no restatement of the title, and every clause carries information an agent needs.

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?

With no parameters and no output schema, the description must convey what comes back and what is required — it does both via the balance/burn/runway enumeration and the scope requirement. Minor gaps remain (units of balance/burn/runway, whether values are current or cached), but nothing blocks a correct call.

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?

Zero parameters, so the schema has nothing to document and there is nothing for the description to compensate for — the specified baseline of 4 applies. No parameter guidance is needed or missing.

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 resource (the signed-in account) and enumerates the exact data returned (balance, hourly burn, runway). The sibling list is entirely instance/offer/SSH-key oriented, so this tool is trivially distinguishable from every neighbor without opening a schema.

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 implies the usage context (fetching your own account state) and gives a real prerequisite — a key with user:read and billing:read scopes — but never states when to call this versus anything else or what conditions make it inapplicable. Adequate but thin.

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