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

Annotations already declare readOnly/idempotent/openWorld, and the description adds meaningful behaviour: data is read live from a public catalogue, results are capped at 8 brands in browse mode, and the payload includes price, list price, saving, duration, delivery type and a brand link. With no output schema, this carries the return-shape burden well.

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, no filler, front-loaded with the purpose before the two behavioural modes. Every clause carries information the agent cannot get from the structured fields.

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 3-optional-param read tool with no output schema, the description covers source, scope, result cap and returned fields adequately. The only real omission is how it relates to the sibling compare_plans when an agent must choose between them.

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%, so the baseline is 3, but the description adds real meaning: 'brand' selects the per-plan vs per-brand return shape, and 'category' only applies in the without-brand branch. Country scoping by store and currency is reinforced beyond the schema's own note.

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 resource (Fleek prices for digital subscriptions) and a specific action (find/return deals), then splits behavior into the with-brand and without-brand cases. An agent can tell this is a catalogue lookup rather than a comparison tool. It stops short of naming a sibling like compare_plans to sharpen the contrast.

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?

Explicitly describes the two invocation modes: supplying a brand returns that brand's plans, omitting it returns up to 8 brands optionally narrowed by category. Country defaulting ('omitted means Fleek's global store, in USD') is also spelled out. No guidance on when to prefer this over compare_plans.

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