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

Annotations already declare readOnly=false, idempotent=true, destructive=false, and openWorld=false, so the safety profile is covered. The description adds genuinely new behavioral context with 'Send only what changes', telling the agent that omitted fields are preserved rather than cleared. It says nothing about validation failures or what the response confirms.

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?

Three short sentences, with the operations front-loaded and the id source and partial-update rule following in order of need. No sentence is 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?

For a three-parameter mutation with no output schema but with annotations covering safety and idempotency, the description supplies the two things the schema can't: where ids come from and that updates are partial. Missing only edge-case behavior (invalid title length, response shape), which is minor here.

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 only 33%, so the description has to carry weight, and it does: it names the two mutable fields in plain language, identifies where subtask_id originates, and 'send only what changes' explains the optionality semantics of done/title. It still leaves the effect of an explicit false versus an omitted done to inference.

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 and resource and enumerates the two supported mutations ('tick done or not done, or rename it'), so the agent knows exactly which subtask fields are in play. It does not explicitly distinguish itself from the sibling update_task (task-level edits) or add_subtask, leaving that boundary implicit.

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?

'Subtask ids come with each task in get_today and get_tasks' gives concrete prerequisites and routes the agent to the sibling tools that produce valid ids. 'Send only what changes' clarifies the expected call pattern, though no explicit when-not-to-use or exclusion versus update_task is offered.

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