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

Annotations only declare the mutation/safety profile; the description adds substantial context beyond them: nobody is messaged, matching/dedup by email or phone, the name-only re-save exception, the atomic 2000-contact cap failure, and per-contact validation failure isolation. The idempotentHint=false annotation is consistent with the stated re-save behavior, not contradicted.

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?

Long but densely packed with no filler; it is front-loaded with the when-to-use rule before the mechanics. Each sentence carries a distinct constraint (routing, batch size, validation, dedup, cap), though slightly more could be tightened.

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 need not be explained, and the description still covers limits, atomicity, side effects, validation behavior, and dedup rules. Nothing an agent needs to call this correctly is absent.

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 field formats are already documented, but the description adds real meaning: the 1-50 batch constraint, the requirement of at least name/email/phone, and the dedup key semantics. These go beyond the structured schema without fully compensating for anything missing.

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)') and immediately distinguishes the tool from siblings by name. An agent can separate saving contacts from inviting guests without opening any 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?

Gives an explicit trigger ('when the user wants people saved... without inviting them to an event now') and names the alternatives for the contrasting case ('to invite people, use lemonvite_add_guests or lemonvite_invite_contacts'). Both when-to-use and when-not-to-use are covered.

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