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

With no annotations, the description carries the full burden and does well: it explicitly declares the read-only profile ("no writes, no deletes, no quota spend, no email") and discloses an auth nuance most tools omit ("ACL is not consulted; usage_get, usage_periods_list, and budget_get were ungated reads"). It falls short of a 5 only because it says nothing about rate limits, error behavior, or failure modes.

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 and dense, with the three views presented in a consistent pattern and the read-only/safety note placed after the functional content. The repeated "Returns X, Y, Z" cadence is slightly mechanical and longer than strictly necessary, but every sentence carries usable 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, the description compensates by enumerating what each view returns (usage totals/budget view/current flag; periods/hasMore/currentPeriodYm; budget/keyBudget), which is the key missing structured data. It is nearly complete, lacking only error/edge-case behavior for an unknown view or empty period.

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 coverage is 100% and the schema already spells out each parameter's meaning, defaults, and cross-view ignoring (e.g. limit default 12/max 100, cursor format). The description largely restates that information rather than adding new semantics, so baseline 3 applies.

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 this account's usage and quotas") and immediately decomposes the resource into three named views (summary, periods, budget) with their scopes. Naming estimate_usage and manage_billing as the adjacent tools makes it distinguishable from siblings 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?

Gives explicit conditions per view: view=summary for one calendar month with the periodYm-omit rule, view=periods to page stored months, view=budget for quotas and checkout URLs. It also names the alternatives and their trigger points ("Choose estimate_usage before a spend, and manage_billing to pay"), which is exactly the routing an agent needs.

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