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

Annotations already declare the write, non-destructive, idempotent and closed-world profile, so the description need only add what they cannot. It adds the save_search_results routing but says nothing about duplicate handling, whether existing leads are skipped or merged, or whether contact data is required per lead — material for a bulk-insert operation.

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 short, front-loaded sentences with no filler; the routing hint comes before the parameter note. The telegraphic style leaves a little ambiguity, but nothing is wasted.

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 and thin schema descriptions, an agent still lacks the essentials for a bulk write: what a successful call returns, how many leads actually landed, and what happens to duplicates or invalid entries. What is present is correct but not sufficient for confident invocation.

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 only 33%, so the description has to compensate and does so partially: 'Extra fields belong in lead_data' clarifies why the nested arbitrary object exists rather than encouraging extra top-level keys (which additionalProperties:false forbids). It still says nothing about list_id, the required shape of a lead entry, or the 1–100 item bound enforced by 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 ('Save supplied contacts in a list'), which maps directly onto the tool name and separates it from read/export siblings. It does not spell out that entries go into an existing list identified by list_id, but the intent is unmistakable.

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?

Names one explicit alternative with a condition ('Use save_search_results for paid Dievio results'), which is genuinely useful routing. However, it gives no guidance on the other common cases in this sibling set: when to use it versus create_list/get_list_leads, or whether the target list must already exist.

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