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

Annotations already cover the safety profile (destructiveHint=true, idempotentHint=false, openWorldHint=true, readOnlyHint=false), so the bar is lower. The description still adds real context: the operation is triggered by a human pressing Send and requires a one-time token issued to the card, which tells the agent the call is not freely repeatable.

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?

Two tight sentences with the action and the trigger front-loaded, and no padding. Slightly compressed wording ('the one-time token the card was given') costs a little clarity but nothing is wasted.

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 non-idempotent, destructive email send with no output schema, the description covers the trigger and the auth token but says nothing about failure modes (expired token, already-sent invoice) or the relationship to send_invoice. Enough to attempt the call, not enough to use it confidently.

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%, so the description must carry parameter meaning. It explains sendToken as a one-time token the card was given, which is useful, but invoiceId is left entirely to the schema's uuid format with no explanation of which invoice qualifies.

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 specific verb (emails) and resource (the invoice shown on a TapTax send card) to its client, which is more precise than the bare title. It implicitly separates itself from the generic send_invoice sibling via the card context, but never names that sibling, so the differentiation is left to inference.

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 triggering condition ('when the person presses Send on that card'), which is genuine usage context. However it never states when to use this instead of the sibling send_invoice, nor what to do if the card/token is stale, so the guidance is implied rather than explicit.

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