Contact Labels: Add Labels

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

Annotations only say readOnly=false, idempotent=false, destructive=false; the description adds meaningful context beyond them by disclosing that existing labels are overwritten, the exact POST endpoint, and the required User API key header (api-access-token). It also explains extra_body for unlisted fields. It stops short of describing error or empty-list behavior.

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 action and its replace semantics, followed by endpoint, auth, body, then encoding notes. It is a dense patchwork rather than prose, and the Persian/Arabic-Indic digit note is long, but every line carries operational information.

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 mutation tool with no output schema, the definition covers endpoint, auth, body fields, replace behavior, and the extra_body escape hatch. Missing only edge cases (what an empty label list does, validation/label-existence errors), which keeps it short of fully complete.

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 baseline is 3; the description earns extra credit by naming the body field (labels), explaining extra_body merge behavior, and noting that text values are sent unchanged while IDs/numbers may use Persian or Arabic-Indic digits. Those notes add real invocation meaning not present in 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?

The description gives a specific verb+resource ('Set the labels of a contact') and, critically, spells out replace semantics: 'Replaces the contact's existing labels with the given list.' This clearly separates it from gapify_list_contact_labels, though it never explicitly names siblings like gapify_set_conversation_labels. Note the title ('Add Labels') conflicts with the body ('Replaces'), which could momentarily confuse an agent.

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?

Usage is implied: call this when you want the contact's label set to equal the supplied list. The replace-vs-append behavior is the key when-to-use signal and it is stated. However, no alternative tool is named and no precondition (e.g., label must already exist) is given, so guidance stops at implicitly adequate.

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