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

Annotations already declare readOnly/ idempotent/ non-destructive, and the description adds substantial context beyond them: which tiers are refused by purchase_data with a 503 not_yet_deliverable and nothing charged, that dag_manifold_30d delivers its API key inline, and that grade purchases are conditional on measured-grade availability. This is exactly the extra behavioral context a listing tool needs.

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 purpose and price basis are front-loaded in the first clause, then caveats follow. It is dense and enumerates many tier names, which makes it sprawl slightly, but each clause carries decision-relevant information (what is purchasable, what is refused, what to buy instead) rather than filler.

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?

No output schema exists, so the description carries return-value burden; it conveys the concept of products-with-prices and refusal states well, though it does not describe the shape of the returned list (fields, ordering). For a zero-param listing tool this is close to complete.

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 zero parameters, so there is nothing for the description to document; the baseline for a no-param tool is 4. Schema coverage is moot here since the object is empty.

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 opening sentence states a specific verb (browse) and resource (purchasable products) with pricing units ($1 = 1 credit). It further disambiguates against siblings by stating the five paid analytics tools are not products here and that several listed tiers are not purchasable. An agent can distinguish this from purchase_data or get_data_dictionary without opening any 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?

Explicit sequencing: 'Call after register_agent' tells the agent the prerequisite order. It also states alternatives ('buy dag_manifold_30d instead' of dag_pro) and directs to check /v1/credits/pricing before buying. When-to-use and exclusion conditions are both present.

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