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 value beyond that: admin/feature gating, the approved-template validation step, and the error surface (`template_not_found`). It does not say whether label_ids removal is reversible or what a success response contains, keeping it out of 5 territory.

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 the purpose in the first two words, then a single explanatory sentence, then bolded prerequisites. No filler. Slightly dense with three clauses in one sentence, but every clause describes a distinct routing aspect.

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 destructive, nested-object mutation with no output schema, the description supplies the prerequisites, the validation/error behavior, and the scope of change, which is most of what an agent needs. Remaining gaps are minor: response shape and partial-update semantics for the nested object.

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 description coverage is only 50%, so the description has to carry weight. It frames the nested lead_form fields collectively (routing, labels, WhatsApp template) and clarifies template validation, but adds nothing for template_language, and the 'replaces the current list' semantics for label_ids is already in the schema. Adequate but not compensatory.

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?

Specific verb (Update) plus resource (a lead form's routing), followed by an enumeration of exactly what the routing controls: lead routing on/off, contact labels, and the WhatsApp follow-up template. This distinguishes it cleanly from the read-side siblings get_facebook_lead_form and list_facebook_lead_forms.

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 real prerequisites (Administrators only, requires the facebook_marketing feature) and a conditional behavior (template is validated against the inbox's approved templates when WhatsApp routing changes). It does not explicitly name sibling alternatives or say when not to use this versus update_facebook_ad_account or sync_facebook_lead_forms, so it stops short of a 5.

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