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

Annotations already declare readOnlyHint/openWorldHint=false, yet the description adds three things they cannot: the members.manage permission gate, the fact that only *active* customers are returned (a real filtering behavior), and that results include untrusted public-written text that must not be treated as instructions. That last point is unusually valuable behavioral context for an agent.

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?

Four short sentences: what it does, how to call it, what it requires, and how to treat the output. Zero filler, with the lookup constraint front-loaded before the safety caveat.

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 does tell the agent what results contain (member-authored public text) and the active-only scope, which covers the main unknowns. It does not say what happens when no match is found or which fields are returned, leaving a small gap for a lookup tool.

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 only 33% — account_id is documented, email and person_id are not. The description compensates by naming both lookup keys, stating they are mutually exclusive ('exactly one'), and clarifying that email must be an exact match rather than a prefix/fuzzy search. It does not supply format hints for person_id, but the schema's uuid pattern already covers that.

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 ('Look up one active customer') plus the two accepted lookup keys and the scope ('active', 'in the account's People directory'). It implicitly separates itself from the list_people sibling by emphasizing 'one', but never names the alternative explicitly.

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?

'Supply exactly one lookup field' is an explicit invocation rule, and 'Requires members.manage' gives a prerequisite an agent must check before calling. It stops short of routing the agent (e.g., 'to enumerate customers use list_people'), so no exclusion guidance is present.

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