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

Annotations already declare readOnly, idempotent, and closed-world behavior, so the safety profile is covered. The description adds genuinely new behavioral detail the annotations don't carry: matching is case-insensitive and a miss returns no contact ('if it exists'). It says nothing about auth or rate limits, but that is a minor residual gap.

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 sentences with no filler: what it does, what it returns, and where to go instead. The alternative routing is placed last, after the core identity is established, so the opening is properly front-loaded.

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 an output schema present, return values need no explanation, and the description covers matching semantics and the alternative tool. The only thing left implicit is the exact not-found behavior, which is implied by 'if it exists' rather than stated.

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% for the single email parameter, so the baseline would be 3. The description goes beyond the schema by specifying that the comparison is case-insensitive, which is real matching semantics an agent cannot infer from 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 ('look up') and resource ('CRM contact by email'), and immediately distinguishes itself from search_leads and from the ID-based get_contact/list_contacts siblings. An agent can tell which tool handles an email-keyed lookup 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?

Explicitly routes broader name/company/stage/phone searches to search_leads, which is the key disambiguation an agent needs. It does not mention the get_contact (by-ID) path, so the 'when not' guidance is strong but not exhaustive.

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