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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds only the qualifier 'reusable,' hinting contacts can be shared across domains, but says nothing about what is returned on an invalid handle or whether lookup is scoped to the account.

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 eight-word sentence with the resource and the lookup key front-loaded. Nothing is wasted and nothing is buried.

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?

The tool is simple (one required param, read-only) and an output schema exists, so return values need no explanation. However, with 0% schema coverage the description should at least say where a contact handle comes from, which it omits.

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 0%, so the sole parameter 'contact_handle' is undocumented in the schema. The phrase 'by its handle' tells the agent the parameter is a contact handle, but adds no format, source, or validity information beyond the field name.

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 ('Get one reusable contact') plus the lookup key ('by its handle'), so the agent knows this is a single-record fetch rather than a list. It does not name or differentiate itself from siblings like list_contacts or get_customer, 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?

Usage is only implied: fetch one contact when you already have a handle. There is no explicit statement of when to prefer this over list_contacts, nor any note that the handle must come from a prior create_contact or list_contacts call.

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