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

With no annotations beyond a title, the description carries the full burden. It discloses the behavioral nature: it is a read-only check that returns information about notification reachability and device list. The phrase 'whether... and on which devices' implies a query with no side effects, which is transparent. However, it does not explicitly state safety (e.g., read-only) or that it makes no external calls, but the context is clear enough.

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 zero filler. The main statement is front-loaded ('Whether this account can be reached by notification at all, and on which devices') and the usage hint follows. Every word contributes meaning, making it concise and well-structured.

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 zero-parameter tool with no output schema, the description is nearly complete. It states what the tool checks and when to use it, which covers the essential information an agent needs to call it correctly. It could be slightly more explicit about the return format, but given the simplicity and the sibling tools, this is arguably sufficient. The lack of output schema is compensated by the description's clear indication of what information is returned.

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?

The tool has zero parameters, and the schema is an empty object with 100% coverage. According to the baseline, 0 params earns a 4. The description adds no parameter details nor are any needed. It appropriately describes the tool's behavior without referencing nonexistent parameters.

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 what the tool does: checks whether an account can be reached by notification and on which devices. It uses a specific scope ('this account') and distinguishes itself from the sibling 'notify_send' by framing itself as a pre-check before promising to notify someone. The purpose is unambiguous and differentiates from the obvious alternative.

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 description explicitly advises using this tool 'before promising to tell somebody something', which provides a clear usage context. It does not explicitly name the alternative (notify_send), but the implication is strong and the guidance is actionable. It lacks explicit when-not-to-use statements, but for a simple query tool this is sufficient.

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