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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds genuine context beyond that: the email precedence rule, the concrete field set returned, and the underlying endpoint (GET /v3/contacts/details). It omits what happens on a miss (empty result vs. error) and any auth expectations.

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 compact sentence front-loads the lookup key and follows with the returned fields; nothing is padded. The trailing endpoint reference is arguably redundant for an agent but is short and aids mapping to the API.

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?

For a two-parameter read tool with no output schema, listing the returned fields plus the endpoint makes it callable without guesswork. Only edge-case behavior on a missing contact is unspecified.

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% and the schema already documents the precedence rule for secondary_email, so the description mostly restates it. Neither parameter is marked required, and the description does not clarify that at least one email must be supplied, which is the one semantic gap worth noting.

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 ('One contact'), the lookup key (primary or fallback secondary email), and the fields returned (name, title, phones, company, departments, custom fields). This clearly separates it from the sibling desk365_list_contacts, which would be the multi-record alternative.

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?

Gives a concrete selection rule between its two parameters: use primary_email, and fall back to secondary_email only when the primary is unknown. It does not say what to do when the email is unknown entirely (e.g., use desk365_list_contacts to search by name), so the alternative routing is left implicit.

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