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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so safety is covered; the description still adds value by stating 'Returns before → after', telling the agent the response is a diff. It stops short of clarifying partial-update semantics (whether omitted fields are left untouched) or whether a failed match errors, which are meaningful for a mutation tool.

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 short lines: purpose plus return shape, then when-to-use, then when-not-to-use. Front-loaded and every clause carries routing or behavioral information; nothing is padding.

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 an 8-parameter mutation with no output schema, the description covers the intent, the mutable field set, the return shape and the sibling boundaries. The gap is that partial-vs-full replacement semantics and target identification via 'client' versus 'ref' remain unstated, which an agent would want before calling.

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 25%, but the description compensates by naming six of the eight parameters (name, email, mobile, period type with both enum values, tags, reference) as the updatable fields. The one residual ambiguity is whether 'ref' supplies a new reference value or identifies the client alongside 'client', which the text does not resolve.

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 opening sentence names a specific verb (changes) and resource (one Client) and enumerates the mutable fields, including the period_type enum values. It also explicitly separates itself from archive_client and pause_nudges, so an agent can pick it over siblings without reading schemas.

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?

Explicit 'Use this when: a Client's details change' plus a 'Not for' line routing the agent to archive_client and pause_nudges for those adjacent intents. Both the affirmative and negative conditions are stated, leaving nothing to inference.

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