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

With no annotations supplied, the description carries the full burden and does so: it discloses cost ('1 CRD (platform credit) per call'), the non-obvious billing rule that a rejected call still bills while a 429 RATE_LIMITED is free, and the need to quote request_id from error results. These are exactly the operational facts an agent cannot infer from the schema.

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?

Three dense sentences, front-loaded with purpose and ordering before the filter semantics and then cost/error handling. Every clause carries information not available in the structured fields; nothing is repeated from the schema.

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, and the description compensates by describing the shape of key return fields (price as a dollar string, credit_type_ids and its [] meaning) as well as error behavior and billing. For a four-parameter read tool with payment-path complexity, nothing an agent needs to invoke it correctly is missing.

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 coverage is already 100%, so the baseline is 3, but the description adds genuine meaning: it explains the response-side semantics of credit_type_ids and what the empty array implies, and clarifies that credit_type_id expands matches to include all-type tiers, plus the UUID validation rule behind the 400.

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 ('List active pricing tiers (credit packs)') plus two distinguishing traits: ordering ('cheapest first') and price format ('price is a dollar string'). Against siblings create_pricing_tier / update_pricing_tier / delete_pricing_tier, the 'list active' verb makes the read-only scope unambiguous.

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 concrete context for using the credit_type_id filter ('returns every tier purchasable for that type: tiers scoped to it plus tiers with []') and the 400 failure mode. It stops short of naming alternatives, e.g. list_credit_types for discovering the IDs you would pass here, so the routing to a sibling is left implicit.

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