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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds nothing beyond that: it never mentions that a single-use, human-approved approval_id may be required, nor any duplicate-checking behavior despite a contacts.duplicates.check sibling.

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?

Two short sentences with the trigger front-loaded before the effect. The first is a sentence fragment and the example is slightly loose, but there is no wasted text.

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 not be described, and only contact_id is required. Still, for an 8-parameter mutation the description omits meaningful context: the approval_id single-use approval flow and duplicate-address handling are both unaddressed.

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 the schema already documents all eight parameters. The description only lightly reinforces two of them (the label mapping to `name`, the street in the example), which is baseline behavior when the schema does the heavy lifting.

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 states a specific verb and resource ('Adds it to the contact') and identifies the label concept, so an agent knows this creates an address record on a contact. It does not distinguish itself from the sibling addresses.update for edits, which keeps it from a 5.

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 a concrete trigger scenario ('When the user gives you someone's address, like "Maya moved to 123 Main St"'), which is real usage context. However it names no alternatives or exclusions — nothing about when to prefer addresses.update, or what to do if the address already exists.

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