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

Annotations only declare readOnlyHint=false, destructiveHint=false and openWorldHint=false. The description adds material behavior the annotations cannot convey: creation is non-idempotent ('New calls create new identities even for the same name'), remote eligibility and allowance checks run through the existing service, and an authorization constraint on the credential type. This is exactly the extra context the annotations leave open.

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, then prerequisites, then the non-idempotency warning and the recovery pointer. Dense and mostly waste-free, though the eligibility/allowance sentence and the auth sentence could be tightened without losing meaning.

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?

Return values are covered by the output schema, so the description correctly spends its budget on what the schema lacks: authorization requirements, duplicate-creation behavior, scope boundaries versus Sites/Scans, and per-field meaning. Nothing needed to invoke this correctly is missing.

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 must compensate, and it names all five parameters (name required; websiteUrl, industry, description, knownBrands optional) plus a semantic distinction the schema cannot express: knownBrands are descriptive facts rather than Sites. It still leaves the nested knownBrands item shape (name/websiteUrl) and URL format expectations to the schema, so it is strong but not complete.

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 states a specific verb and resource with scope: 'Create one Client organisation in an agency Account.' It explicitly separates itself from the many other create_* siblings by naming what it does not create ('this tool creates no Site, association or Scan'), so an agent can distinguish it from create_site or add_competitor without opening 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?

It states prerequisites (requires a nonblank name, requires Account access), a hard exclusion (a Client-restricted credential cannot create a new Client), and a recovery path for ambiguity ('after uncertainty inspect list_clients before repeating'), naming the sibling to use. When-to-use and when-not are both explicit rather than implied.

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