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

With no annotations provided, the description carries the full burden, and it does useful work: "List" implies a safe read, and the qualifier "indicative" on crypto_prices is a genuine caveat telling the agent those figures are not executable quotes. The volume-discount note also describes the shape of the data. It stops short of mentioning auth requirements or whether the bundle catalogue is static.

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, front-loaded with the resource and its returned fields, then a single pricing-structure note. Every clause carries information an agent would otherwise have to discover by calling the tool.

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 zero-parameter, read-only catalogue tool with no output schema and no annotations, the description covers the resource, its return fields, and the pricing relationship. The only gap is that a caller comparing crypto pricing is told the values are indicative but not what to call to get firm rates.

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 disambiguate; baseline 4 applies. The description adds no parameter noise, which is correct here.

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?

Specific verb + resource ("List purchasable credit bundles") and it enumerates the fields returned (USD price, price_per_credit, crypto_prices per asset), so the agent knows exactly what it gets. It does not explicitly distinguish itself from near-neighbours like get_rates or get_credits_balance, which keeps it short of a 5.

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?

Usage is only implied: the word "purchasable" and the price-per-credit detail suggest this is the tool to call before buying credits or comparing bundle economics. There is no explicit when-to-use, no prerequisites, and no named alternative for cases where the agent wants exchange rates (get_rates) or an account balance (get_credits_balance).

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