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

Annotations only declare readOnlyHint=false and destructiveHint=false. The description adds genuinely non-obvious behavior: idempotency with alreadyExisted: true returned instead of an error, name uniqueness per property, and that keywords are stored as text and matched against GSC queries. This exceeds what structured fields disclose.

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?

Front-loaded with the core action and effect, then the idempotency rule and sibling routing. Every clause earns its place with no filler.

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?

An output schema exists, so return format need not be spelled out, and the description still highlights the alreadyExisted flag. It omits permission/scope requirements and behavior on invalid input (e.g., empty or oversized keyword lists), leaving minor gaps for a write 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 coverage is 0%, so the description must carry parameter meaning. It explains name (unique per property, with the already-exists consequence) and keywords (stored as text, matched against GSC queries); siteUrl's role is only implied by "on a property" and the 1000-keyword ceiling is left to the schema.

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+resource+effect: "Creates a topic cluster on a property by grouping keywords under a name." It distinguishes itself from update_topic_cluster and list_topic_clusters by scoping to creation/grouping, so an agent can route without opening the schema.

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?

Explicitly names the alternative ("Use update_topic_cluster to change an existing cluster's keywords") and states the condition that selects it, plus the idempotent already-exists case so the agent knows a duplicate call needs no retry.

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