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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, closed-world, so the safety profile is covered. The description still adds real value beyond them: the metric window is fixed at a rolling 24 months, and calling it without auth will trigger a sign-in flow rather than fail silently. It doesn't mention result truncation or how the 20-default/50-max limit behaves at scale.

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?

Two sentences, both front-loaded: the trigger condition comes first, the returned metrics second, and the auth prerequisite last. The metric enumeration is dense but each item is a distinct capability, so it earns its space. A slightly tighter phrasing could have trimmed a few words.

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 an output schema present, return-value structure needn't be explained, and annotations cover safety. The description completes the picture with the metric scope, the fixed 24-month window, and the auth prerequisite. The only gap is how limits and the supplier filter behave at the edges, which is minor for a read-only tool.

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 both 'limit' (max 50, default 20) and 'supplier' (case-insensitive name filter) fully documented in the schema. The description adds no further parameter guidance, such as how the supplier filter matches partial names. Baseline 3 applies when the schema does the heavy lifting.

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 names a specific verb+resource pairing ('get supplier performance') and enumerates exactly which metrics come back: rolling 24-month on-time rate, fill rate, actual vs. promised lead time, spend, invoice price accuracy, and open/overdue PO counts. None of the sibling tools cover supplier-level analytics, so the agent can distinguish it from get_inventory_overview or list_purchase_orders 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?

It gives an explicit trigger: 'Use this when the merchant asks how suppliers are performing.' It also flags the prerequisite (a connected Forthcast store, with a sign-in prompt). It stops short of naming when NOT to use it or pointing at an alternative for, say, raw PO listings, which would be needed for a 5.

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