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

Annotations already declare destructiveHint=true, readOnlyHint=false and idempotentHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: this is a partial update where 'only the fields given change', and an active trigger is a blocker/precondition rather than something silently overwritten. It does not discuss reversibility or permissions, but that is a modest gap given the annotation coverage.

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, front-loaded with the action and the precondition, zero filler. The merge rule ('only the fields given change') is stated before the edge-case handling, which is the right order for an agent scanning for constraints.

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 10-parameter mutation with no output schema, the description covers the essential decision points: which triggers are eligible, that updates are partial, and the sibling to call for the on-state case. It does not describe the response, so an agent gets no confirmation of what comes back, but nothing critical to invoking it 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?

Schema coverage is 80% and the schema already documents app_id, trigger_id, flow_id, page_name, entity_name, phone_field, whatsapp_bot_id and message_template. The description's enumeration (page, entity, fields, message, number, flow) loosely groups the same parameters and adds the optional-merge semantics, but contributes no syntax or format detail the schema lacks. 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 (change/update) and resource (a WhatsApp trigger) and enumerates the mutable aspects: page, entity, fields, message, number, flow. That maps cleanly onto the sibling set (create_whatsapp_trigger, disable_whatsapp_trigger, list_whatsapp_triggers) without naming them all, so an agent can place it, but the differentiation is implied rather than stated.

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 a real precondition ('a trigger that is switched off') and points at disable_whatsapp_trigger as the alternative for the blocking case. The phrasing 'is turned off first with disable_whatsapp_trigger' is slightly ambiguous about whether the agent must call disable itself or this tool handles it, which keeps it below a 5.

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