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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds context about depending on the user's saved Deckodex targets and the conditional rarity breakdown when set is provided, which are not conveyed by annotations or schema alone.

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 sentences with no filler. The primary purpose is front-loaded in the first sentence, and the second sentence adds a conditional detail without redundancy. It is concise and well-structured.

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 tool is read-only with three optional parameters and no output schema. The description explains the core functionality, the dependency on saved user settings, and the conditional behavior of the set parameter. While return format is not specified, the absence of an output schema makes this less critical. Overall, the description is sufficient for an agent to understand the tool's purpose and likely invocation.

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 all three parameters (set, mode, source) are documented in the schema. The description adds extra meaning for the set parameter by noting it triggers a rarity breakdown, which goes beyond the schema's simple 'Set code' explanation. This is a meaningful addition.

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 verb ('How complete'), resource (signed-in user's collection per set), and distinguishes from siblings like my_collection and my_collection_value by focusing on per-set completion status and cost-to-finish. It also mentions the optional rarity breakdown with the set parameter, adding specificity.

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 through the description of what the tool computes, but there is no explicit statement of when to use this vs alternatives like my_collection or my_collection_value. No exclusions or alternative routing is provided, so the agent must infer the appropriate context.

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