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

With no annotations present, the description carries the full behavioral burden and excels: it warns that v0 sends no email, states that delivering the card is the agent's responsibility, notes the free-tier hard cap, and details validation constraints for relationship and fact_confirmed. This goes well beyond the structured schema.

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 front-loaded with the core action, then delivers critical caveats in short, scannable lines. Every sentence adds unique value—free-tier limits, no-email behavior, relationship handling, and fact confirmation rules—with no 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 10-parameter tool with no output schema, the description gives enough operational context to invoke correctly: catalog-source IDs, the card_url result, no-email delivery, and special parameter semantics. Some details like error behavior or what happens after the free cap remain implicit, leaving room for improvement.

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 0%, but the description compensates by saying all IDs must come from catalog tools and by giving explicit semantic guidance for relationship and fact_confirmed. It does not individually describe occasion, sender_name, recipient_email, or holiday_id, but these are relatively self-evident.

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 opens with the specific verb 'Send a Dear Human card', which clearly distinguishes it from the catalog/preview siblings. It also emphasizes that no email is sent and that the result's card_url is the card, making the tool's purpose unmistakable.

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?

Useful context is provided: IDs must come from catalog tools, first 5 cards are free, and relationship/fact_confirmed modes are explained. However, it never explicitly says when to use send_card versus preview_card or any other alternative, so the exclusion/alternative guidance is implied rather than stated.

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