Pricing

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuine value beyond that: it explains the two pricing modes (output-based vs GPU-based), the per-billing-unit/currency format, the API-key requirement, and that custom pricing/discounts may apply based on account status.

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 core pricing explanation is front-loaded and earns its place, and auth is clearly flagged. But the four-item 'Common Use Cases' bullet list and the link are largely filler that restates obvious scenarios without adding routing or behavioral information.

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 two-parameter read tool with no output schema, the description is fairly complete: it explains return semantics (per-model billing unit in a given currency), covers the pricing-mode nuance, and states the auth requirement. Only the ambiguity against estimate_pricing keeps it from being fully 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?

Schema description coverage is 100%: the schema already documents endpoint_id filtering syntax (1-50 IDs, comma or array) and the account label. The description adds no parameter-level detail, so baseline 3 is correct because the schema does the heavy lifting.

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 and resource ('Returns unit pricing for requested endpoint IDs') and explains the pricing semantics well. However, it never differentiates itself from the close sibling estimate_pricing, so an agent cannot tell from the description alone which of the two to call.

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?

The 'Common Use Cases' list gives implied usage context (UI display, comparison, cost tools), but it reads as generic marketing rather than routing guidance. There is no explicit when-to-use-this-vs-alternative statement, and the obvious alternative estimate_pricing is never mentioned.

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