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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial non-obvious behavior: which tiers are priced but not purchasable, that purchase_data will return 503 not_yet_deliverable for them, and that grade purchases are conditional on measured-grade availability. This is exactly the kind of consequence-level disclosure annotations cannot express.

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?

Purpose and pricing are front-loaded, and the long middle sentence about unpurchasable tiers carries genuinely load-bearing information rather than filler. It is denser than it strictly needs to be, packing several product names and caveats into one block, but nothing is redundant.

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 parameterless listing tool with a full annotation set and no output schema, the description supplies everything an agent needs to call it correctly and to interpret the credit pricing and purchasability caveats. Return shape is not described, but the safety annotations and pricing context make that a negligible gap.

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 per the rubric the baseline is 4. The description introduces no additional parameter detail (none exists), and none is needed for a parameterless lister.

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 ('Browse purchasable products with prices in credits') and immediately clarifies the credit-to-dollar rate. It is clearly distinct from purchase_data and check_balance in intent, but it never explicitly contrasts itself with the potentially-overlapping list_datasets sibling, so an agent must infer the boundary.

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?

Gives a concrete sequencing rule ('Call after register_agent') and a pre-purchase instruction ('check /v1/credits/pricing before buying'), which steers usage well. It stops short of naming the alternative tool to use when the task is not browsing products (e.g., list_datasets), so the when-not guidance is incomplete.

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