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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely new context: a `full_access` API key is required and the exact REST endpoint and operationId are given, which helps an agent diagnose auth failures and reason about the call surface.

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?

Very short and front-loaded with the action, then the prerequisite and endpoint. The operationId/"Contacts" tag metadata is arguably noise for tool selection, but overall there is little waste.

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 and annotations covering safety, the description is close to sufficient, but for a lookup tool it omits what is returned and what happens when the contact does not exist (404 vs. empty), which an agent needs to plan error handling.

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 only 50%: id_or_email is well documented in the schema, but audience_id has no description at all. The endpoint template `GET /audiences/{audienceId}/contacts/{idOrEmail}` partially compensates by showing both parameters' roles, but the meaning/constraints of audience_id remain unstated.

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?

"Retrieve a contact" is a verb+resource but is essentially a restatement of the tool name and title, and the added endpoint path does most of the disambiguating work. It never distinguishes this single-record fetch from siblings like list_contacts, update_contact, or the audience-scoped variants.

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?

No guidance on when to use this vs. list_contacts (bulk) or get_audience. There is a hard prerequisite (a `full_access` API key), but that is an auth constraint rather than a when-to-use rule, and no exclusions or lookup-fallback behavior are stated.

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