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

With destructiveHint=true already declared, the description earns credit for disclosing the real behaviors that matter: fields are only sent when passed, emails/phones accumulate rather than overwrite, and custom_fields requires membership_type or the API rejects it. It does not cover permissions or rate limits, but it adds substantial context beyond the annotation.

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?

Five short sentences, front-loaded with the core action and the highest-risk caveats (partial send, additive emails/phones, custom_fields requirement) before the endpoint reference. No filler.

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?

For a 9-parameter mutation tool with nested objects and no output schema, the description covers the confusing behaviors an agent would otherwise get wrong. The only real gap is not stating that tag_list replaces existing tags, though the schema field description does say 'Replacement tag list.'

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%, so the baseline is 3, but the description adds genuine meaning beyond the schema: the additive (not replacing) nature of emails/phones and the membership_type prerequisite for custom_fields. That interpretation guidance is not derivable from the field descriptions alone.

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 ('Update fields on an existing member'), which cleanly separates it from create_member, get_member, and update_opportunity among siblings. It does not explicitly name a sibling to avoid, but the resource scope is unambiguous.

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?

Gives clear operational context: partial-update semantics ('Only the fields you pass are sent'), that emails/phones are additive rather than replacing, and the coupling of custom_fields with membership_type. It stops short of naming when to prefer a different tool, but the conditions for correct invocation are well stated.

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