read sync usage and balance

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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them by explaining the polymorphic response: credits when credit-billed, freeMonthlyLimits when free-tier, usage only when both are null and only when totals are not reported as incomplete. It also discloses the authorization rule for canManageBilling (billing must allow it and caller must be owner or admin), which is behavior an agent cannot get from the schema. Nothing here contradicts the readOnlyHint.

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?

Front-loaded with the primary purpose, then the response-shape rules, then a compact 'not for' list. Dense but every clause carries information an agent needs, since the output schema alone does not tell you which branch is populated. It is long for a zero-parameter read, and the conditional-field sentence is packed tightly enough that it requires careful reading.

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?

An output schema exists, so return values need not be enumerated, yet the description supplies the missing interpretive layer: which of credits/freeMonthlyLimits/usage is populated under which billing mode and when usage stays null. For a zero-param read with rich conditional output, this is exactly the context needed to interpret results correctly.

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 (additionalProperties: false, empty properties), so there is no parameter meaning to add and the baseline of 4 applies. The description compensates by describing how the response shape varies, which is the only input-adjacent ambiguity (which billing mode the org is in).

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 and resource ('Read what the connected sync. organization has left to spend in the current billing period') and immediately distinguishes itself from three named siblings with different scope. An agent can tell this apart from account_get-context or generations_get-costs 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?

Contains an explicit exclusion block naming the alternative for each adjacent need: past generation cost → generations_get-costs, new-work quote → generations_estimate-cost, plan limits and org → account_get-context. It also closes off side-effect expectations (buys no credits, changes no plan, starts no generation), leaving nothing to infer.

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