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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is known. The description adds behavior beyond that: deduplication by email within the campaign and malformed addresses being counted as `invalid` rather than rejected. It leaves ambiguous whether dedup applies against existing campaign leads or only within the batch.

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 no filler; the batch limit and retry instruction are front-loaded before the dedup/invalid caveats. Every clause carries information an agent needs.

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 carries the burden of explaining the response, and it only implies result counters by saying malformed addresses are 'counted as invalid' without saying what counts are returned (added/duplicates/invalid). The call-critical facts (batch cap, dedup key, invalid handling) are present, but the result contract is left to inference.

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 50%, and the description only touches the email field (the dedup key and the malformed-address case). It adds nothing about campaignId or the optional lead fields (tags, customFields, customFieldTypes), so it neither fully compensates for the coverage gap nor falls below the baseline for a schema that documents most fields.

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 ('Add ... leads to a campaign') with an explicit scope ('1-100') and keys on the identifying field (email). It is clearly distinguishable from siblings like bulk_add_lead_tags, update_lead, and delete_leads.

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?

'call again for more' gives concrete batching guidance that tells the agent how to handle more than 100 leads. It does not name an alternative tool or a when-not-to-use condition, but the batch size cap plus the retry instruction covers the main usage decision an agent faces here.

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