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

The description goes beyond the readOnlyHint annotation by adding a critical behavioral note: 'A contact grants no access on its own — it is a convenience, not a permission.' This prevents misuse by clarifying that retrieved contacts are not authorization tokens, adding real behavioral context that annotations alone do not convey.

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: the first front-loads the purpose with examples, and the second adds a crucial caveat. Both sentences earn their place; there is no filler or redundancy.

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 tool with no parameters and a simple read operation, the description is adequate. It states what is returned (the workspace address book) and adds the permission caveat. It could be slightly more specific about the fields in the address book, but that is not essential for a correct call.

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, so the schema fully covers everything. The baseline for 0 params is 4, and the description correctly focuses on the resource and meaning rather than inventing parameter details.

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 explicitly states the tool returns the workspace address book and gives example questions it answers ('what is this client's email address?', 'who do I have saved?'). This clearly identifies a specific verb ('returns') and resource (address book) and distinguishes it from sibling tools about transfers, collections, folders, and guests.

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 implies usage when contact information is needed, but does not explicitly state when to use this tool vs. alternatives like get_account or list_guests, nor does it provide exclusions. There is no guidance about when not to use it, so usage guidance is implied rather than explicit.

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