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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: case-insensitive substring matching, a 50-result cap sorted by name, a total match count, and the scoping fact that only the connected account's own contacts are searched. It stops short of a 5 only because some return-shape detail is duplicated in the output schema.

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 primary use case, then matching behavior, result limits and scope, with sibling routing at the end. Mostly every sentence earns its place, though the description is on the longer side and the return-limit sentence slightly overlaps the output schema.

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?

Given a single optional parameter, rich annotations and an output schema, the description supplies everything an agent needs: triggers, matching semantics, result limits, fallback behavior when there are more than 50 matches, scope restrictions, and sibling alternatives. Nothing critical 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 description coverage is 100% and the single 'query' parameter is fully documented in the schema, including that omitting it lists from the top. The description restates the same matching semantics ('matches any part of a contact's name, email or phone, ignoring case') without adding format or edge-case detail beyond the schema, so the 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 specific verb and resource (search contacts / address book) and immediately differentiates the tool from siblings by naming lemonvite_invite_contacts, lemonvite_remove_contacts and lemonvite_list_guests. An agent can tell exactly what this does and how it differs from the other contact/guest tools.

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 concrete trigger phrases ('find Alice in my contacts', checking whether a contact is saved) and explicitly names the downstream tools whose inputs it feeds (invite/remove contacts need contact_ids). It also routes the agent elsewhere with 'To see who is on an invitation, use lemonvite_list_guests.' Both when-to-use and when-to-use-something-else are covered.

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