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

Annotations declare readOnlyHint=true, so safety is covered. The description then adds behavior the annotations cannot express: the empty-state returns a note rather than an error, and the caller must follow the returned guide. It does not cover scoping/auth or rate considerations, but the empty-state disclosure is genuinely useful.

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 sentences, each load-bearing: what it returns, when to call it, and what to do on the empty case. The purpose is front-loaded and there is no filler.

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?

With no output schema, the description still tells the agent what comes back (the guide, or a note when unset) and what to do with it. The chain into the outreach craft skill fallback closes the main gap; only a fuller description of the returned guide's structure is missing.

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 single parameter on_behalf_of is fully documented in the schema (100% coverage), including its source (list_agency_clients) and default behavior, so the schema carries the load. The description adds nothing about it, which matches the baseline-3 rule for high coverage.

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 and resource ('Return the user's personalization guide') and immediately defines the resource's content ('how they want a person researched before you write to them'). This scope is clearly distinguishable from near-siblings like get_writing_style_guide, get_skill_guide, and get_user_memory.

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?

Explicitly gates invocation ('Call this only when you are going to personalize a message') and specifies a fallback path when the resource is empty ('fall back to the default research rules in the outreach craft skill'). Both the when-to-use and the when-empty alternatives are named, leaving nothing to inference.

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