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

Annotations already declare readOnlyHint=true, and the description adds behavioral context beyond that: it describes the possible return states (card last4/name or PENDING) and clarifies this is an optional check, not a required step. This is useful context not present in the annotation.

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 description is concise but complete: every sentence adds value—optionality, return behavior, usage guidance, and argument mapping. It is front-loaded with the purpose and avoids fluff.

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 simple read-only lookup tool with an output schema, annotations, and a clear usage note, the description fully covers when and why to use it. It also communicates the normal workflow context without needing to explain return values in detail.

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 input schema already provides 100% coverage with descriptions for bill_id and user_id, so the description's phrase 'the user_id and bill_id to look up' adds little beyond what the schema states. Baseline 3 is appropriate.

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 clearly states a specific verb and resource: 'check whether the user has finished the secure form and a card is on the bill yet.' It also explicitly distinguishes its role from sibling tools by referencing the normal path (analyze_bill -> user fills form -> confirm_payment_intent), making its niche unmistakable.

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?

Provides explicit when-to-use guidance: 'Use only if you need to confirm the card landed (e.g. the user asks) - it is not a required step.' It also names the normal workflow and thus implicitly tells when not to use it.

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