rules_lookup

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the tool is safe and idempotent. The description adds valuable behavioral context by specifying the return format (full text, parent context, subrules), which is not covered by 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 concise at two sentences, front-loaded with the action, and contains no unnecessary words or redundant information. Every sentence adds value.

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 no output schema, the description adequately explains the return format (full text, parent context, subrules). It covers both query methods (number and keyword) and mentions the optional section narrowing. It is complete for a lookup tool, though it omits possible pagination or result limits.

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?

Input schema has 100% description coverage, so each parameter is already documented. The description adds minimal additional meaning beyond what the schema provides, such as mentioning 'number or keyword search' which mirrors the query parameter description.

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 verb 'Look up', the resource 'MTG Comprehensive Rules', and the two methods: by number or keyword search. It also specifies what is returned (full text, parent context, subrules). This distinguishes it from sibling tools like rules_interaction or rules_scenario.

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 provides basic guidance on how to use the tool (by number or keyword) but does not explicitly state when to use it versus siblings like rules_interaction or rules_scenario. There are no exclusions or alternative recommendations, leaving ambiguity for the agent.

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