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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description adds the return payload scope and a useful privacy guarantee ('contact details are never returned'), but it never explains what makes this destructive (e.g. whether omitted fields are left untouched or wiped) or what happens on a stale expectedLastEditTime beyond the schema's own note.

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?

Three tight sentences: trigger, return shape, exclusion, each earning its place with no filler. The return-value sentence overlaps the output schema slightly but also carries the non-obvious privacy statement, so it is not pure 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 an output schema present the return summary is a bonus rather than a necessity, and the annotations cover safety. The one real gap is partial-update semantics — whether fields not supplied are preserved — which matters for a destructive-flagged mutation but is absent from both description and schema.

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%, so all six parameters are documented in the schema itself. The description only restates the set of editable fields and adds no format or constraint detail beyond that, which is the correct baseline when the schema does the heavy lifting.

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?

The description opens with a specific verb plus resource ('change a member's name, phone, email or language') and enumerates the mutable fields, so an agent immediately knows what the tool does. It also explicitly separates itself from the create path with 'Not for adding a new member,' which disambiguates it from the create_member sibling.

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?

It gives a clear trigger condition ('Use this when someone asks to change...') and one explicit exclusion (adding a new member). It stops short of naming create_member as the alternative or noting the prerequisite that memberId and expectedLastEditTime must first come from list_members, though the schema descriptions cover that.

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