num_cards_due_today

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

No annotations are present, so the description carries the full burden. It discloses that the tool returns a count and supports an optional deck filter, but does not specify whether the operation is read-only, what happens with invalid deck values, or any side effects. The description is adequate but lacks 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 sentence that front-loads the action and resource, with no unnecessary words. Every part earns its place, making it efficient and direct.

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 the tool's simplicity (one optional parameter, output schema exists), the description is complete. It explains what the tool does and the parameter's role. Since an output schema is present, it need not describe return values. No gaps are evident.

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?

The input schema has 0% description coverage (no natural language for parameters), so the description must compensate. It adds 'optional deck filter,' which explains the sole parameter's purpose. This provides meaning beyond the schema typedef, though it could be more specific about valid values or behavior.

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 tool's purpose: to get the number of cards due exactly today, with an optional deck filter. The verb 'Get' and specific resource 'number of cards due exactly today' provide a clear, actionable purpose that distinguishes it from siblings like fetch_due_cards_for_review, which likely retrieves the actual cards.

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 usage (when you want a count of due cards) and mentions an optional filter, but does not explicitly guide when to use this tool versus siblings like fetch_due_cards_for_review or other tools. It lacks exclusions or context for when not to use it.

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