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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully confirms the underlying REST call (GET /contacts/{id}) and enumerates the returned field groups, but adds no pagination, error, or auth context.

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 tight sentences with the purpose front-loaded and the REST endpoint as supporting detail. No wasted words, though the endpoint string is arguably redundant with the tool name.

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 no output schema, the description compensates by naming the default fields (name, company, role, emails, phone numbers) and flagging custom fields. Enough for an agent to know what comes back from this simple single-param read.

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?

Only one parameter exists and the schema documents it at 100% coverage ('The contact id.'). The description restates the id requirement without adding format, prefix, or sourcing guidance, 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?

States a specific verb and resource ('Get a single contact by its id') and enumerates the returned field groups. It distinguishes itself from the list_contacts sibling only implicitly via 'single', so it stops short of an explicit differentiation.

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?

The phrasing 'by its id' implies the precondition for use (you already hold a contact id), but there is no explicit when-to-use statement and no named alternative for lookup by other means (e.g. list_contacts or a search tool). Usage is inferred rather than stated.

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