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

Annotations already establish a safe, read-only, closed-world read. The description adds real domain behavior beyond that: amounts are netted of refunds, card and custom processors carry processing fees and a resulting deposit figure, and cash has no fees. That is meaningful disclosure about what the numbers mean, though it says nothing about permissions, rate limits, or result shape.

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?

Three sentences, front-loaded with the core purpose and followed by the examples and the consistency note. No filler, though the final sentence about Financial Summary is somewhat incidental to invoking the tool correctly.

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?

There is no output schema, so the description usefully compensates by naming what comes back per payment method: netted totals, processing fees, and deposit amounts. Combined with the 100% schema coverage on inputs and the read-only annotations, an agent has enough to call it 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?

Schema description coverage is 100%, so startDate, endDate, outlets and stations are all already documented in the schema, including the inclusive-day semantics. The description adds no date-format, timezone, or outlet/station filtering detail beyond what the schema provides, so the 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, resource and scope: how customers paid over a date range, netted of refunds. The quoted example questions ('how much came in on card vs cash', 'what did processing fees cost me') pin down exactly what dimension of the data this tool reports, distinguishing it from a generic sales or transaction list.

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 paraphrased user questions give clear positive-use context, and the note that this is the same aggregation the Financial Summary settlement section uses tells the agent when the two should agree. It does not, however, explain when to prefer hub_get_sales_breakdown or hub_get_transactions instead, so there is no explicit exclusion.

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