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

Annotations already cover read-only, idempotent, closed-world safety, so the description's job is to add what annotations can't — and it does: valuations are Slabline-derived from comparable sales, individual sale rows are not returned, and a free-text query resolves to the top match. It does not say what happens when neither parameter is supplied or when no match is found.

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, front-loaded with the return payload, then the invocation mechanics and the non-obvious caveat about underlying sale rows. Nothing is repeated from the schema or title.

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?

With no output schema, the description does its job by naming the three value components and clarifying that raw sale rows are not included. The remaining gap is failure-mode behavior — no result, ambiguous query, both parameters given — which matters for a zero-required-parameter tool.

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 100%, so the baseline is 3, but the description adds real meaning beyond the schema: the slug is authoritative and comes from search_cards, and query resolution uses the top match rather than requiring exactness. What it omits is the interaction when both are passed, or when neither is.

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 ("Get one card's current Slabline value") and enumerates exactly what comes back: graded value, raw/loose value, across-grades total. This is clearly distinguishable from the sibling search_cards, which returns matches rather than a valuation.

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 routing context: take a slug from search_cards, or fall back to free-text if no slug exists. It does not state any when-not-to-use condition (e.g., that bulk valuation requires repeated calls or that it should not be used for discovery), so it stops short of explicit exclusions.

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