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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds genuine value by warning that the autocomplete may return non-commander cards and that only the primary field is validated, which tells the agent to distrust secondary results.

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 tight sentences with the core purpose front-loaded and the caveat followed by the downstream hint. The phrase "only the primary field is validated as a supported Commander choice" is slightly convoluted but earns its place as a warning.

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 single-parameter, read-only search with no output schema, the description covers purpose, result-quality caveat, and intended downstream use. It could still note result limits or matching behavior, but nothing essential to a correct call 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% for the single query parameter, so the description must carry the weight. It conveys that the query is a name and recommends an exact name, but says nothing about length bounds, fuzzy matching, or how partial names behave — leaving the parameter only partly characterized.

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 ("Find Commander candidates by name") that an agent can immediately distinguish from the sibling search_cards tool. It doesn't explicitly name search_cards as the alternative, which keeps it short of a 5.

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?

It implies when the tool applies (finding a commander before build_mana_base) and adds the constraint to use the exact commander name for that downstream call. However, it never contrasts this with search_cards or states when not to use it, so usage is only implied rather than spelled out.

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