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

Annotations already declare readOnly=true, idempotent=true, destructive=false, and closed-world, so the safety profile is fully covered by structured data. The description adds no behavioral context beyond the 'full details' framing and does not clarify what 'full details' includes versus the card/digest siblings. No contradiction with annotations.

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, efficient sentence with no redundancy. It is slightly front-loaded on the 'when' clause rather than the 'what', but nothing is wasted.

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?

With an output schema present (return values need not be explained) and annotations fully covering the safety profile, the description is largely complete for a single-parameter read tool. The residual gap is sibling disambiguation against contacts.card.get and contacts.digest.get.

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 coverage is 100% and the single contact_id parameter is fully documented in the schema. The description adds no syntax, format, or edge-case meaning beyond what the schema already provides, 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?

The description states a clear outcome: retrieving the 'full details of one specific contact' identified by API id. The verb is implied via the title/name (Get). It does not, however, differentiate itself from adjacent siblings such as contacts.card.get or contacts.digest.get, which also retrieve per-contact detail views.

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 offers a condition for use ('when you need the full details of one specific contact and you have their API id'), which implies the retrieval use case. But it names no alternatives and gives no exclusions, so an agent cannot tell when to prefer this over contacts.card.get, contacts.digest.get, or contacts.list.

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