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

Annotations already flag destructive=true and idempotent=true; the description adds the crucial detail the annotation cannot convey — that it is a partial patch ('only the fields you pass are sent') but that tags and customFields are wholesale replaced. It omits what happens if contact_id does not exist and whether a malformed custom field erases existing values, keeping it below 5.

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?

Four short clauses, front-loaded with the 'WRITE:' marker, then semantics, then safety advice, then endpoint. No sentence is 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 37-param destructive update with no output schema the description covers the essentials: mutation type, partial-update semantics, the two replace-not-merge fields, and a verification step. Still missing error/nonexistent-id behavior and whether the updated record is returned.

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?

With 37 parameters and only 35% schema description coverage, the description should compensate more. It does address the two highest-risk collections (tags and customFields are replaced as given) and the partial-update rule for the other 35 fields, but the remaining booleans (allowSms/allowEmails/allowPhones) and id-reference params are left to 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 and resource ('change fields of an existing contact') and even names the HTTP method and path, so an agent can distinguish it from pobuca_create_contact. It does not explicitly contrast with the sibling updater (pobuca_update_organization), but the resource word 'contact' does that work implicitly.

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?

'Look the contact up first and confirm the right one' is concrete pre-call guidance that points at pobuca_get_contact/pobuca_list_contacts without naming them. No explicit exclusions (e.g. 'use create_contact for new contacts'), so it stops short of full routing guidance.

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