List labels

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that by naming the required token scopes, the MESSAGING task and the accepted Page Contact Terms, plus the fact that labels tag threads in the inbox label view.

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?

Two sentences, no filler. The core listing behavior and its psid variant come first, and the auth constraints follow, which is the right order for an agent deciding whether it can call this.

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?

Return fields (id and name) are stated despite there being no output schema, and the auth prerequisites are fully enumerated. Pagination is delegated to the schema, and edge cases such as an empty label list are not covered, but nothing essential to a correct call 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 description coverage is 100%, so psid, after, limit and profile are already documented in the schema. The description only restates the psid behavior ('the labels on one person') and adds nothing about cursor, limit or profile semantics, so the 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 (List) and resource (the Page's custom Messenger labels), plus the exact shape of each item (id and name). It also carves out the psid variant, which clearly separates it from create_label, delete_label and assign_label in the sibling set.

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 explicit context for both modes: no psid = all Page labels, with psid = labels on one person. Prerequisites (Page token, pages_manage_metadata, MESSAGING task, Page Contact Terms) tell the agent when the call will fail, but no sibling is named as an alternative.

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