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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety bar is met structurally. The description adds genuinely new behavioral context: rows in held or expired state carry no confirmed price, which prevents misreading a blank price as free. It omits any note on result ordering or size, but no output schema exists and the return shape (price, context limits, sources) is summarized.

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, zero padding, with the scope and provider list front-loaded and the state caveat immediately after. Nothing repeats the title verbatim and every clause carries information an agent would otherwise have to guess.

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 three-parameter read-only lookup with no output schema, the definition covers what is returned, which providers, and the crucial state semantics. The remaining gap is routing against sibling cost/plan tools, which would make it fully self-sufficient.

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%, so all three parameters (model, provider, current_only) are already documented with examples and the 'omit to list all' default. The description's mention of 'current' state reinforces current_only but adds no syntax or format detail beyond the schema. Baseline 3 applies when the schema does the parameter work.

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 description names a specific resource and scope: 'Current per-token API prices for the AI models Kingy verifies (OpenAI, Anthropic, Google)'. It also states what accompanies the price (context limits, official sources). It does not explicitly distinguish the read-only lookup from siblings like estimate_api_cost or compare_subscription_plans, so sibling differentiation is left implicit.

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 purpose is implied as a price lookup, and the note that only 'current' rows have a confirmed price hints at when rows are meaningful, but the description never says when to use this versus estimate_api_cost (cost projection) or compare_subscription_plans. No explicit exclusions or alternative routing is given despite several adjacent tools.

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