client_getContactDeviceCount

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

With no annotations, the description carries the full burden. It transparently explains the counting logic (WaWeb connections plus phone) and provides a concrete example. It doesn't disclose edge cases, errors, or permissions, but for a simple get operation this is acceptable.

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?

The description is two sentences with no fluff. It front-loads the core purpose, then adds a clarifying example. Every word earns its place.

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 simple get tool with no output schema, the description adequately explains the return value by defining device count and giving an example. It could be more explicit about the return type or error conditions, but overall it is sufficient.

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 100% for both parameters (sessionId and userId), so the schema fully handles parameter documentation. The description adds no additional parameter meaning, which is fine but not exceptional.

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 description clearly states the tool's function: 'Get user device count'. It specifies the resource (device count) and verb (get), and distinguishes it from sibling tools as the only one for device counting. The example clarifies the exact meaning of the count.

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?

Usage context is implied through the description and tool name, but there is no explicit guidance on when to use this tool versus alternatives or any exclusions. The description gives insight into the output semantics but not when to invoke it.

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