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

Goes well beyond the annotations by disclosing data quirks an agent must handle: all plans share the same feature set, they differ only in monthly newsletter emails and storage, Solo's yearly price is null, and every plan begins with a free trial requiring a card at Stripe. That last point is real behavioral context since it implies a payment obligation. No return format or ordering is given, and the annotations' destructiveHint=true sits oddly next to readOnlyHint=true, but the description itself does not contradict them.

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?

Four short sentences, front-loaded with the resource and then the differentiating facts an agent needs to present the data. Nothing is padding, though the feature-parity fact and the per-plan differences could be phrased in a single sentence.

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 carries the burden of describing what comes back, and it largely does: a set of plans, uniform features, differences in emails and storage, and a null yearly price for Solo. Missing only ordering, currency, and the exact price field shape, which the agent will discover at call time.

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?

The tool takes no parameters, so there is nothing to disambiguate; the description correctly spends no space on argument syntax. Baseline 4 applies for a zero-parameter tool.

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?

Names the resource specifically ('PixelGlass's plans and prices') and the verb is unambiguous from the title/name pairing. It distinguishes itself from nearby billing siblings by focusing on the catalog rather than a checkout or link action, though it never names those siblings.

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?

'Show these to the person and let them choose' is an explicit usage directive telling the agent to display the result rather than act on it. It stops short of naming the follow-up tools (start_checkout, billing_link), so the transition from listing to purchasing is left implicit.

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