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

Annotations already indicate readOnlyHint=false, destructiveHint=false, idempotentHint=true. Description adds valuable extras: 'CONSUMES ENRICHMENT CREDITS per call', 'Requires an API key', and clarifies in-place update and no duplication. It also mentions returns the lead. No contradiction with 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?

The description is two paragraphs with purpose first, then usage and cost details. It is not overly long, though could be slightly tightened. Every sentence adds necessary context (fields, usage sequence, credit consumption, return behavior).

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?

Given the simple interface (1 parameter, no output schema, annotations provided), the description adequately covers when to use, cost, side effects, and what it returns. It doesn't describe the return format, but that's not critical for this simple tool.

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% (leadId described as 'Lead UUID from list_leads'), so description doesn't need to add much. It reinforces to use after list_leads, but does not significantly augment parameter meaning 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?

The description clearly states the tool's function: 'Fill in a saved lead's missing person and company detail' and lists specific fields (seniority, department, LinkedIn, phone, company size, industry). It distinguishes itself from siblings like list_leads or search_leads by focusing on enrichment of a single saved lead.

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 concrete use guidance: 'Use it on one lead at a time, after list_leads has given you its id, and typically before writing outreach.' Also advises checking first to avoid wasting credits. It does not name alternative tools explicitly but frames when it's appropriate relative to lead flow.

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