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

Annotations already declare write/destructive/non-idempotent behavior, and the description adds useful context that no message is sent and that the new contact is returned. However, it does not warn about the practical consequence of destructiveHint=true / idempotentHint=false — namely that repeated calls may create duplicate contacts.

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?

Four short clauses, front-loaded with the WRITE marker and required parameter, with zero filler. Every sentence earns its place.

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 21 parameters, no output schema, and rich annotations, the description covers the essentials: required field, key identity fields, no-message side effect, and return value. The one notable gap is duplicate-creation guidance for a non-idempotent create.

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?

All 21 parameters are documented in the schema (100% coverage), so the schema does the heavy lifting. The description adds a little meaning by flagging first_name as required and recommending mobile/email for reachability, but does not explain the many optional fields (vip, unsubscribed, archived, hidden) that carry behavioral weight.

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 ('WRITE: create a contact') and explicitly names the underlying GraphQL mutation `createContact`, making it distinguishable from siblings like superphone_update_contact and superphone_find_contact without inspecting the 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?

Includes an actionable constraint ('add a mobile number or email so it can be reached') and clarifies a boundary ('Creating a contact does not send it a message'), implicitly routing messaging to send_message. It stops short of naming update_contact as the tool for existing records, so it's clear context rather than full when/when-not guidance.

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