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

Annotations already establish readOnly, idempotent, non-destructive. The description adds the auth requirement (`read` scope), the UTC default, and the rationale for excluding the current day—useful context beyond the annotations, though no return semantics are given.

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 core purpose, then defaults and prerequisite; every sentence carries information. Slightly dense but 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?

For a read-only, single-parameter diagnostic tool with no output schema, the description fully conveys what it does, when it applies, and the auth precondition. Only the returned drift-report shape is left implicit, which is a minor 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?

Schema coverage is 100% and the single `day` parameter is already documented with its pattern and default. The description's restatement of the default and why today is excluded adds rationale but little new parameter syntax, so the baseline of 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 (re-derives and compares usage) on a specific resource (one day's request log vs the billed daily rollup). The 'drift report' framing and the one-day scope clearly separate it from spicrawl_usage and spicrawl_usage_summary.

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 clear context: use it to check whether the rollup missed or double-counted usage, and warns that today would always show drift, steering the agent to a completed day. It does not, however, explicitly name the aggregate sibling tools it complements.

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