compare_units

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

With no annotations, the description carries the full burden. It discloses the output content ('Shows stats, weapons, abilities, and keywords'), which is useful. However, it does not mention default behavior for game_mode, validation of unit names, or error handling. The description is neither misleading nor rich in behavioral detail.

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 a single, front-loaded sentence that immediately states the action, scope (2-4 units), and what it shows. No wasted words, and every element contributes to understanding 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?

The description covers the core purpose and output contents, which is essential given no output schema. It omits details like game_mode defaults or input validation, but those are documented in the parameter schema. Overall, it is sufficiently complete for a simple comparison 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 description coverage is 100%, so the schema already documents both parameters (units array with min/max, game_mode enum with descriptions). The tool description adds no additional parameter semantics beyond what the schema provides, so the baseline of 3 is appropriate.

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 a specific action ('Compare') on a concrete resource ('2-4 Warhammer 40K units or Kill Team operatives') and lists the displayed attributes (stats, weapons, abilities, keywords). This distinguishes it from sibling tools like lookup_unit and search_units, which focus on single lookups rather than side-by-side comparison.

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 implies the use case: comparing multiple units/operatives side by side. However, it does not explicitly mention when to use this tool instead of alternatives like lookup_unit or search_units, nor does it provide any exclusions or conditions. The context is clear but the guidance is not explicit.

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