cost_reduction_check

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

The description reveals precise behavioral details beyond the readOnlyHint, openWorldHint, and idempotentHint annotations: it reduces only generic costs, leaves colored pips, hybrids, {C}, and {X} untouched, and clarifies that multiple reducers don't apply to colored portions. No contradiction with annotations.

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 two concise sentences plus a rule reference, all front-loaded with the core action. No filler—every sentence adds value, including the rationale for using the tool.

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?

Given the presence of annotations and full schema coverage, the description sufficiently covers the tool's purpose and handling of edge cases (e.g., hybrid mana, {X}). It lacks an explicit description of the output format, but the 'detailed' vs 'concise' parameter provides insight.

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?

With 100% schema coverage, the baseline is 3. The description does not significantly augment the schema's parameter descriptions; it only references the reducer_card's role. The schema's own descriptions are adequate for the parameters.

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 the tool applies a cost reducer mechanically and reports what it does not reduce. This specific verb+resource (apply cost reducer) distinguishes it from sibling tools like rules_interaction or combat_calculator, which handle different aspects of Magic.

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?

The description explicitly advises using this tool instead of prose to avoid arithmetic errors, with a concrete example of past mistakes. It explains the rule's limitation (only reduces generic component). However, it does not explicitly state when to use an alternative, though the context is strong.

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