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

Annotations already declare non-read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds the ownership constraint and the concurrency guard, which is real context. However, it never states whether this is a partial update (omitted fields left untouched) or a full replace, which is the key behavioral question for an 11-field update 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?

A single front-loaded sentence with the verb, resource, and constraint in the right order, and zero filler. It is arguably undersized for an 11-parameter mutation tool, but nothing in it is wasted.

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 a mutation tool with 11 parameters, 18% schema coverage, and no output schema, one sentence leaves major gaps: no partial-vs-full update semantics, no note on what a successful response contains, and no differentiation from create/upsert. An agent could call it but would be guessing at edge behavior.

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 18% — just id and expected_updated_at are described, and the description merely repeats the expected_updated_at hint. The nine optional mutable fields (name, email, notes, phone, address, company, contact_id, message_language, reminder_cadence) get no explanation of update semantics or formatting beyond their names and enums.

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 (Update) and resource (invoice_client) plus an ownership scope. It does not distinguish itself from close siblings like invoice_client_upsert or invoice_client_link_tenant, so an agent must infer the boundary, but the core action is unambiguous.

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?

The 'you own' qualifier implies a precondition and the compare-and-set mention hints at when to pass expected_updated_at, but there is no explicit when-to-use versus upsert/create guidance. Usage is implied rather than stated.

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