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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds useful context beyond annotations: the tool is scoped to the signed-in user, behavior differs with and without arguments, and cardNumbers aggregate across all printings. It does not describe output format or edge cases, but the annotation coverage lowers that burden.

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, front-loaded with the core resource, and uses a clear conditional structure for the two invocation modes. Every phrase adds information; there is no repetition or filler.

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 simple read-only tool with one optional parameter and no output schema, the description covers the main invocation modes and what the user can expect to get back. Minor gaps remain, such as the exact shape/format of the returned totals and completion data, and overlap with sibling tools is not addressed.

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 low, but the description compensates by explaining what cardNumbers does: it returns how many copies of each requested card the user owns, combining all printings. The schema already provides the format example and array constraints; the description adds the aggregation semantics and the no-argument mode.

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 what the tool does: it reads the signed-in user's collection and provides totals, per-set completion, or owned copies for given cardNumbers. It is specific about behavior based on arguments, but it does not explicitly distinguish itself from siblings like my_set_completion, which likely overlaps on the per-set completion aspect.

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 gives explicit usage context: call with no arguments for totals/completion, or with cardNumbers for per-card copy counts. It does not, however, mention when to prefer alternative tools such as my_set_completion or my_collection_value, so it lacks exclusion guidance.

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