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

Annotations already declare readOnly/idempotent/non-destructive, so the description only needs to add what they don't cover, and it does: the tool exposes a spend ceiling for this connection and the point at which the owner is asked for approval. It does not state freshness of the credit figure or whether the call itself costs anything.

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 sentences, front-loaded with what the tool returns, then the invocation triggers. No restatement of the title, 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?

With no output schema and no parameters, the description must convey the return shape, and it does at a useful level (credits, plan, remaining spend before approval). It stops short of specifying units, currency, or how a 'spend today' reset works, which an agent may want when reasoning about limits.

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 there is nothing for the description to disambiguate. Baseline 4 applies; the description correctly spends its words on the returned data instead of inventing input semantics.

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 names the exact payload: credits available, the account's plan, and the per-connection daily spend allowance that triggers owner approval. That is specific enough to separate it from sibling read tools like get_job or get_capabilities, though the action verb ('get') lives only in the name/title rather than the prose.

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?

It gives two concrete trigger conditions: call before paid work (create_image, create_video, quote_job, etc.) and call when a job is refused for credits. That is strong positive guidance, but no explicit when-not or named alternative (buy_credits) is offered for the top-up path.

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