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

Annotations only supply destructiveHint=true, so the description usefully clarifies the semantics: it is an additive write that creates a persistent record, and it discloses that emails/phoneNumbers are stored under default field labels rather than custom ones. It also names the underlying REST call (POST /contacts). It stops short of stating auth requirements, duplicate-handling behavior, or irreversibility.

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 sentences, front-loaded with the action and its persistence consequence, then the parameter nuance, then the endpoint. No filler sentences.

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 9-parameter write tool with no output schema and only a destructiveHint annotation, the description is adequate but incomplete: it never states what is returned on success (e.g., a new contact ID) or how duplicate contacts are handled. The absence of an output schema means the description could reasonably carry that information, and it does not.

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 100%, so the baseline is 3, but the description adds real meaning beyond the schema by explaining that emails and phoneNumbers are passed as simple string arrays and land under default field labels - a constraint the schema does not convey. It says nothing about role/company/externalId, which the schema already documents.

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?

Specific verb+resource ('Create a new contact in the workspace') with scope stated. Every sibling tool in the list is a read operation (get_*, list_*) or send_message, so creation is trivially distinguished from all of them.

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?

No when-to-use or when-not-to-use guidance, and no alternatives or prerequisites (e.g., dedupe against openphone_get_contact / list_contacts before creating) are mentioned. The 'WRITE ACTION' label implies caution but does not route the agent between tools.

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