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

Annotations cover the safety profile (non-destructive, idempotent, open-world), and the description adds real context beyond them: one email per person, no duplicate sends, and a daily cap on emails. It does not explain what happens if the daily limit is hit or what permissions are needed, which keeps it out of 5 territory.

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 key behavior is front-loaded, but the text is a single run-on sentence in a chatty register, and the 'family group' aside is incidental. Every clause carries some information, yet the delivery is looser than it needs to be.

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 no output schema, the description correctly explains the return value (a tap that pre-fills WhatsApp/SMS/mail), and it discloses the dedup and rate-limit guarantees. What is missing is failure handling when the daily email cap is reached, which an agent invoking a sending tool would want to know.

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 coverage is 100%, so both parameters are already documented, and the description mostly restates their effect ('get the taps only and send nothing'). It adds only the framing that the tap is for people with no address, so the baseline 3 is appropriate.

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 names a concrete verb-chain (emails the invitation, hands back a shareable 'tap') and the resource (the invitation/link tied to a book). An agent can tell this is the dispatch step rather than a collection or lookup step, though it never names a sibling like add_people or get_links to sharpen the boundary.

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?

Usage is implied through the schema — the required 'book' handle 'start_book gave you' and the 'also_email' switch — and the no-address case is described. There is no explicit when-not or alternative routing, so the agent must infer that this is the terminal step after people have been added.

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