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

Annotations only supply readOnly/destructive/idempotent/openWorld hints; the description goes well beyond them by disclosing dedup semantics (matched by email or phone, name-only re-saved every time), the 2000-contact cap with all-or-nothing batch rejection, per-contact partial validation failure, and that nobody is messaged. These are the operationally decisive facts an agent needs.

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?

Front-loaded with the routing rule, then batch limits, dedup, and cap behavior in compact clauses. Every sentence carries an operational fact, though the density is near the upper bound for a single-call description.

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?

An output schema exists so return values need no explanation; the description covers scope, alternatives, batch limits, validation behavior, dedup, and the hard cap. Nothing an agent needs to call this correctly is missing.

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% and documents the batch and field limits, so the schema carries most of the load. The description adds genuine value the schema does not: each contact needs at least a name, email, or phone (the item schema has no required array), and that malformed email/phone fails only its own contact.

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 and resource ('people saved to their Lemonvite contact list (address book) for future invitations') and immediately contrasts the scope with sibling tools (lemonvite_add_guests, lemonvite_invite_contacts). An agent can distinguish this from the invite/guest tools without opening a schema.

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?

Explicit when-to-use ('without inviting them to an event now') plus named alternatives and the condition that selects each. It also advises searching before re-saving name-only contacts, giving a concrete pre-call workflow.

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