Card price lookup (free, Scryfall)

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

Annotations already cover readOnly and open-world behavior, yet the description still adds real operational context: it is free, needs no credentials, reads Scryfall bulk-derived data, and is refreshed daily. It stops short of saying how staleness or missing cards are handled, but the annotation bar is already met.

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 compact clauses, front-loaded with the cost/credential signal an agent needs first, then capability, then data provenance. No filler sentences.

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 3-parameter read-only tool with no output schema, the description names the returned price fields and the data freshness, which is most of what an agent needs. The remaining gap is the unexplained 'all_printings' toggle and no note on behavior when a fuzzy match fails or returns multiple cards.

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?

Only 'set' has schema documentation (33% coverage); the description usefully clarifies that 'name' is a fuzzy match and enumerates which price fields come back. However, 'all_printings' is never explained, and the claim of returning 'all printings' prices sits awkwardly beside a parameter that defaults to false, leaving the agent to guess the actual default scope.

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 ('Fuzzy-name card lookup returning all printings' prices') plus the currency fields returned, and names the data source (Scryfall bulk-derived, daily). It is clearly separable from the cardmarket/tcgplayer siblings by source and currency set, though it never explicitly contrasts itself with those price-guide tools.

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?

'FREE tier' and 'No credentials' imply when to prefer this over credentialed price sources, and 'fuzzy-name lookup' hints at the input style. But there is no explicit when-to-use/when-not guidance versus tcgplayer_price_guide or cardmarket_price_guide, which are the obvious alternatives for price data.

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