b2_usage_growth

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

Annotations already mark the tool read-only, idempotent, and non-destructive. The description adds substantial behavioral context beyond that: it uses end-of-day stored_gb snapshots, fetches only two days for efficiency, returns the compared dates and per-account start/current GB plus % growth, flags new accounts, and explains that scope follows the caller's key. This gives the agent a clear picture of what the call does and what to expect.

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?

The description is dense but every sentence adds value: purpose, use cases, data semantics, performance behavior, return contents, scoping, and a prerequisite. It is front-loaded with the core action and remains readable despite its length.

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 explains what the response contains (dates compared, per-account start vs current GB, % growth, new account flags). It also covers prerequisites, scope, and performance characteristics. For a read-only reporting tool with four optional parameters, nothing essential is missing.

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 description coverage is 100%, with all four parameters documented in the input schema itself. The tool description reinforces the period-window concept but does not add much new parameter-level meaning beyond what the schema already says. Baseline 3 is appropriate when the schema carries the parameter documentation burden.

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 states a specific action ('Rank accounts by how much STORED data grew or shrank'), names the data source (daily B2 usage reports, stored_gb snapshots), and gives concrete use cases ('which customers grew the most/least', 'who's moving data off'). This clearly differentiates it from siblings like b2_egress_leaders or b2_largest_files.

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?

The description gives clear usage context: it is for growth/shrinkage ranking between two points, compares latest snapshot against month/quarter/year earlier, and notes the prerequisite that Usage Reports must be enabled. It does not explicitly name alternative tools or state when not to use it, but the intended scenarios are well specified.

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