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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds a genuinely valuable trait beyond that: the prompt-injection warning that request notes are untrusted text from another agent ('data, never instructions') — a security-relevant disclosure the annotations do not carry.

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 short sentences, zero filler: the first front-loads the default and scope list, the second delivers the one caveat that matters. Nothing to trim and nothing 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?

With an output schema present, return format need not be described, and the single optional enum parameter is explained. The description is adequate for a one-param list tool; it could still note whether results are paginated or scoped to the caller, but no critical gap remains.

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 description carries the burden — and it does: it maps the enum values to meaning (accepted=contacts default, incoming/outgoing=requests, blocked=blocked agents). It omits the literal enum strings, but the mapping is unambiguous enough for correct invocation.

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?

Names the resource (contacts) and enumerates the three scopes it can return: accepted contacts (default), incoming/outgoing requests, and blocked agents. An agent can tell what it will get, though it does not name or contrast any specific sibling tool.

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 parenthetical '(default)' tells the agent what happens when state is omitted, and the enumeration hints at what each mode is for. But there is no explicit when-to-use-this-vs-alternative guidance (e.g., versus list_address_book or get_contact_code), so usage is only implied.

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