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

Annotations already declare destructiveHint=true, readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description's added behavioral claims — retrieval and permanent/trash deletion — are not achievable through this schema, so the extra context is inaccurate rather than additive. No PATCH/partial-update semantics are disclosed.

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?

The tool-specific portion is short and front-loaded, with no wasted sentences about the actual update behavior. However, the embedded 'aisa-pricing' boilerplate adds noise irrelevant to tool selection, and the brevity comes at the cost of accuracy rather than precision.

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?

An output schema exists, so return values need not be explained. But for a mutation tool with annotations carrying only the safety profile, the description should clarify idempotency, label-only scope, and non-reversibility; instead it describes capabilities the schema cannot perform, leaving the agent with an incorrect model of the tool.

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 50%, and the nested update body's add_labels/remove_labels constraints (no system labels, remove priority) are documented only in the schema. The description's generic 'modifying labels' neither clarifies that the body is the sole mutation channel nor warns that no other thread field can be patched, and it implies parameters that do not exist.

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 claims three incompatible operations — 'Retrieve, update, or delete an email thread by its ID' — while the schema only accepts a thread_id and an update body containing add_labels/remove_labels, i.e. label modification only. Retrieval and deletion are already covered by sibling tools get_agentmail_thread and delete_agentmail_thread, so the stated purpose actively misroutes the agent rather than distinguishing this tool.

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?

No when-to-use guidance and no alternatives are named, despite a dense sibling set (get_agentmail_thread, delete_agentmail_thread, patch_agentmail_inbox_thread). Worse, the 'fetching thread details' and 'deleting the thread' claims point the agent at the wrong tools for those operations. This is misleading rather than merely absent.

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