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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=false, so the safety and replay profile is covered. The description adds the deduplication workflow constraint, which is genuinely useful context, but says nothing beyond annotations and schema about duplicate-name behavior or what a successful save returns.

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?

A single sentence with the precondition front-loaded and zero filler. Nothing is repeated from the title or the schema, and the actionable part (check find_contacts first) leads.

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 and parameter semantics are fully covered by the schema, so the description only needs to carry intent and sequencing, which it does. The remaining gap is the create-vs-update decision boundary, which matters given update_contact is a sibling.

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%, so every one of the nine parameters, including idempotencyKey and the nested phone/address objects, is already documented in the schema. The description adds no parameter-level meaning, 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 specific action and resource ('save a reusable contact'), which maps cleanly onto create_contact and distinguishes it from the read-side sibling find_contacts. It is framed as usage rather than a direct 'creates a new contact record' statement, so the create-vs-update distinction against update_contact is left implicit.

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?

It gives an explicit trigger condition and prerequisite: only create after find_contacts confirms the contact does not already exist. That is real routing guidance with a named alternative, but it stops short of saying what to do when the contact does exist (update_contact instead), which is the main competing path.

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