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

Annotations already declare readOnly/openWorld/non-destructive, but the description adds real value beyond them: results are 'newest first', pagination totals count all leads in the range rather than the page, and it discloses the auth requirement ('Cotlet API key with access to this app'). It does not mention rate limits, but the added behavioral context is substantial.

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?

It is front-loaded with the purpose, but it repeats the same content twice — 'email enquiries with message and listing' is restated as 'Email leads have the enquirer's message and the listing.' Roughly a third of the text is redundant.

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 usefully explains the return shape (message+listing for emails, time+caller+result for phone) and clarifies the totals semantics. Absent any explicit statement of the return container structure, it is nearly but not fully complete.

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 coverage is 100%, so the schema already documents all five parameters, establishing a baseline of 3. The description adds only a single parameter hint ('Set listing_id to see one property') and no format or enum detail beyond the schema.

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 ('list... leads'), names the source report (ZooplaPro Leads report) and enumerates the two lead kinds it returns (email enquiries, phone calls). An agent can tell exactly what this returns without opening the schema.

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 notes the date-range framing and that listing_id scopes results to one property, which implies usage, but it never explicitly states when to use this tool versus sibling listing/performance tools. No when-not or alternative routing is given.

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