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

No annotations are provided, so the description carries the behavioral burden. It discloses that the comparison is grounded in the person's own spend and reported per year, but it says nothing about the response shape (no output schema exists), whether the call is read-only, or that the 'source' slug is used for click attribution — context that lives only inside the schema. Adequate, not complete.

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 with zero filler: the operation and its result come first, the routing rule second. Every clause earns its place and nothing is buried.

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 an 11-parameter tool with nested objects, no annotations, and no output schema, the description covers intent but leaves the return shape and the read-only nature implicit. It also doesn't mention the prerequisite of mapping spending via spending_categories, which only appears in the totals schema text.

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%, including the non-obvious constraints on totals and the years enum, so the schema does the heavy lifting. The description adds a framing ('two named cards', 'on the person's own spending', annual horizon) but no per-parameter meaning beyond what the schema already says.

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 first sentence names the exact operation — two named cards compared head to head on the person's actual spending — and states the output (which pays more, annual dollar delta). It also explicitly separates itself from simulate_cards, so the agent can distinguish it from siblings without opening a schema.

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 an explicit trigger ('when they are choosing between two specific cards') and an explicit alternative with its own trigger ('what should I get' → simulate_cards). This is the when/when-not/alternative pattern at full strength.

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