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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the description adds the requirement of Id and SyncToken, which is a behavioral prerequisite (must fetch first). However, it does not disclose the sparse update behavior, line replacement semantics, or restrictions on sensitive fields—those are only in the schema description, not the tool description. The description provides minimal behavioral context beyond the annotations.

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 description is a single, concise sentence that front-loads the purpose and the critical prerequisite. Every word earns its place; there is no fluff or redundancy. It is appropriately sized for a tool with a rich schema.

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?

Given the tool's complexity (nested entity object, sparse update semantics, sensitive field restrictions), the tool description is minimal. It covers the core purpose and the Id/SyncToken requirement, but it does not mention the sparse behavior, line replacement, or the need to avoid sending sensitive fields. However, the schema description is comprehensive, so an agent reading the schema will have the necessary details. Still, the description itself is not fully complete for an agent that relies on it as the primary guide.

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 the schema already documents both parameters (entity and company) in detail, including the sparse update behavior, Id/SyncToken requirements, and field restrictions. The tool description itself adds no parameter-level meaning, so the baseline score of 3 is appropriate since the schema does the heavy lifting.

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 states a specific verb ('Update'), a specific resource ('existing time activity in QuickBooks Online'), and the required fields (Id and SyncToken). This clearly distinguishes it from create_time_activity (creates), delete_time_activity (deletes), and search_time_activities (searches). No ambiguity about what the tool does.

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?

The description implies the use case (updating an existing record) and provides a prerequisite (requires Id and SyncToken), but it does not explicitly state when to use this vs. alternatives, nor does it mention that the entity must be fetched first. It lacks explicit when-not-to-use guidance or naming of sibling tools, though the verb and resource make the primary purpose clear.

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