Map an NFC card to a game

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

Annotations already declare idempotentHint=true and destructiveHint=false, and the description reinforces this by explaining the card is never written to and read-only cards/toys work. It also discloses a refusal path (already-mapped cards) and a prerequisite human step, which annotations cannot express. Minor gap: what happens on re-mapping to a different game or an invalid game ref is unstated.

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 short sentences, each carrying distinct information: what happens, who it works with, and how to invoke it. The key constraint (no card writing) is front-loaded.

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?

With an output schema present, return values needn't be described, and the description covers prerequisites, card compatibility, and refusal behavior. It stops short of covering edge cases like an unknown game ref or an already-mapped card being reassigned.

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%, and the schema already explains that omitting uid uses the card scanned in the last 2 minutes. The description restates the omit-uid workflow but adds no syntax or format detail beyond the schema, so baseline 3 applies.

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 concrete verb and resource (map a card to a game) plus the key mechanism: the mapping lives in Zaparoo, not on the card. That mechanism implicitly separates it from the sibling write_nfc_card, so an agent can tell the two apart without reading schemas.

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?

Gives a usable procedure ('Ask the user to scan the card on the game's MiSTer first, then call this without uid') and a condition for failure ('Refuses a card that's already mapped'). It does not explicitly name write_nfc_card as the alternative when the user does want to write to the card, leaving that inference to the agent.

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