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

Annotations already declare readOnlyHint, openWorldHint and non-destructive, so safety is covered. The description adds genuinely non-obvious context: plan-tier gating (Pro sees full contact info and action time/type, other plans see less) and the auth requirement (Cotlet API key with app access).

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?

Front-loaded with what the tool returns and who sees what, and the routing sentence is well placed at the end. It repeats the Pro-tier point ("Pro for full contact info" then "Pro members see full contact info..."), which is minor redundancy but not harmful.

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 read-only list tool with no output schema, the description supplies the missing pieces an agent needs: auth prerequisites, plan-based data differences, filter semantics and sibling routing. Pagination is only implied via the cursor parameter, but the schema covers its mechanics.

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 five parameters are already documented in the schema. The description restates the filter set (interest, industry role, date range) and listing scoping without adding syntax or format detail, so the schema carries the load and baseline 3 applies.

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 (lists leads) and scopes it precisely: leads across all listings or a single listing, filterable by interest, industry role and date range. It also names the sibling tools (get_lead, contact_leads) so an agent can distinguish listing from fetching or contacting.

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 routes the agent: pass lead_id to get_lead or lead_ids to contact_leads, which draws the boundary against alternatives. It does not phrase an explicit 'use this when you want to browse/search leads' condition, so it stops short of full when/when-not guidance.

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