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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the mutation safety profile is covered. 'Send only what changes' adds a partial-update contract, though the schema's single required field already implies the other fields are optional. Nothing is said about what happens to omitted fields or error 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?

Two short sentences, front-loaded with the action and followed by the id prerequisite and update rule. No filler.

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?

There is no output schema, so return values need not be described. The description covers the actions, id source, and partial-update rule, but omits what a caller should expect on failure or how renaming interacts with existing title values, leaving minor gaps for a mutation 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 description coverage is only 33% (just subtask_id), so the description must compensate. It does explain the semantics of the two undocumented parameters (done = tick, title = rename) and confirms id provenance, but adds no format, length, or clearing behavior beyond 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?

States specific verbs (tick done/undone, rename) applied to a specific resource (subtask), and the tool name plus description clearly separate it from add_subtask and update_task. An agent can tell what it does without opening the schema.

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?

It tells the agent where subtask ids come from (the subtasks list of a task in get_today or get_tasks), which is real prerequisite guidance and routes toward the sibling readers. It does not state any when-not condition or contrast against update_task, but the context is clear.

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