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

Adds substantial context beyond the annotations: consumes enrichment credits per call, requires an API key, updates in place and OVERWRITES existing phone/LinkedIn/seniority/company fields, does not create a record, and is idempotent in record terms but still bills on a second run. These details are consistent with destructiveHint=true and idempotentHint=true, and the credit/auth warnings are things annotations cannot express.

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 purpose, then usage ordering, then cost and mutation behavior, so an agent can stop reading early. Slightly padded by restating the no-duplication point twice ('does not create a new record' and 'running it twice does not duplicate'), which costs it the top score.

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?

No output schema, but the description says the updated lead is returned in place, and it covers cost, auth, overwrite semantics and idempotency for a one-parameter mutation tool. Nothing an agent needs to decide or invoke correctly is missing.

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?

Only one parameter and schema description coverage is 100% ('Lead UUID from list_leads'), so the schema already carries the semantics. The description correctly routes the id's origin to list_leads but adds no format or constraint detail beyond that; 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 (fill in / enrich) and resource (a saved lead's missing person and company fields) and enumerates exactly which fields are populated: seniority, department, LinkedIn, phone, company size, industry. An agent can distinguish this from search_leads, list_leads or reveal_company_contacts without opening a 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?

Explicit when-to-use: one lead at a time, after list_leads supplies the id, typically before writing outreach that needs context. It also gives a when-NOT-to: check the lead first because enriching an already-populated lead wastes credits.

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