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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so 'read-only and safe' largely repeats structured data. The description does add scope value by clarifying what is checked (person-level do-not-contact list AND company blacklist), which is useful behavioral context beyond the annotations.

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?

Two tight sentences, with the check scope front-loaded before the usage hint. The safety clause partially duplicates annotations, but no sentence is wasted and it is well-sized for a simple read tool.

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 no-required-param read tool with full schema coverage and no output schema, the description covers inputs and intent adequately. It could briefly state what the check returns (boolean/blocked status), but nothing needed to invoke it correctly 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?

Schema description coverage is 100%, so all three optional parameters are already documented in the schema. The description maps the inputs loosely (contact/company/domain) but adds no syntax, format, or precedence guidance beyond what the schema provides, making the baseline 3 appropriate.

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 (check) and resource (blacklist), and enumerates the three accepted inputs: saved contact, company name, and domain. It is inferable but not explicit that this differs from the sibling list_blacklist, so it stops short of 5.

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?

Provides a clear use context: 'safe to call before adding a lead to a campaign.' It does not explicitly name list_blacklist as the alternative or state when not to use this tool, so it is clear but not fully routing.

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