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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered and the bar is lower. The description adds genuine context beyond that: it is a composite read combining balance-by-source, start-eligibility, ceiling and allowance, and it discloses the decision it supports (dispatch). Auth needs and rate limits remain unstated.

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 the core action and the returned facets, closing with the actionable trigger. No filler, no restatement of the title, and every clause carries distinct information.

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 carries the full burden of describing what comes back, and it does so thoroughly across five value categories. What is missing is minor: no indication of freshness/refresh behavior or any cost of invoking it, though for a zero-arg read-only call that is a small gap.

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, which is the baseline-4 case; there is nothing schema-side to document. No parameter information is needed or missing, so the description is not penalized 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?

States a specific verb ('Read') and resource ('the workspace's credit balance') and enumerates the distinct facets returned: balance by source and expiry, mission-start viability, per-mission ceiling, project allowance, recent usage. That enumeration implicitly separates it from siblings like list_billing_ledger (raw ledger entries) and list_credit_offers (purchasable offers), so an agent can tell them apart 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?

'Check it before dispatching work' gives a clear triggering context for calling the tool. It stops short of naming an alternative (e.g., list_billing_ledger or list_credit_offers) or stating when not to call it, so it is clear context without exclusions.

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