card_lookup

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

With readOnlyHint and openWorldHint already covering the safety profile, the description adds substantial non-obvious behavior: the exact set of returned fields, the existence of unresolved_mentions for unmatched quoted names, and the deliberate no-guessing fallback to candidates on ambiguous input.

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?

Front-loaded with the core purpose and dense with value; nearly every clause adds a distinct fact. The middle sentence is a run-on list ('limit, Genesys points, legality and why not') that is slightly harder to parse than it needs to be.

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?

There is no output schema, so the description must describe the return surface — and it does: full text, stats, per-format legality, alt passcodes, quoted names, rulings links, plus the unresolved_mentions edge case and the ambiguous-input behavior. Nothing an agent needs to invoke and interpret this tool is missing.

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 0% and the single parameter has no description, so the description carries the burden — and it does, explaining that query accepts either a card name or a passcode and how ambiguous values are handled. It stops short of syntax details (case sensitivity, quoting rules) but is well beyond the bare schema.

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+resource ('One card by name or passcode') and enumerates the payload the caller gets back (text, stats, format status, rulings links). It implicitly separates itself from search_cards by scoping to a single card, but never names a sibling, so it falls short of full sibling differentiation.

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?

Usage is implied: this is the single-card lookup, and the note that unknown/ambiguous names return candidates rather than a guess tells the agent the fallback path. There is no explicit 'use this when X, use search_cards when Y' guidance or stated prerequisites.

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