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

Annotations already declare readOnlyHint=false, destructiveHint=true, and openWorldHint=true, so the write/external-system profile is covered. The description adds one genuinely useful behavioral point beyond the schema: due_string accepts natural language including recurrence ('every monday'), which implies recurring tasks get created. It says nothing about persistence, auth requirements, or what happens when project_id is invalid.

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, front-loaded with the core action, with optional fields grouped efficiently at the end. No filler or redundant restatement.

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, and annotations carry the safety profile. For a one-required-param create tool this is largely sufficient, though the description could note account connection and the default-to-Inbox behavior is only in the schema.

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 100%, so the baseline is 3; the description adds a small amount by explaining the priority scale in natural terms (1=normal … 4=urgent), though the schema already carries nearly identical wording including the UI p1=4 mapping. The ignored 'confirm' flag is documented only in the schema, not the description.

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?

Names a specific verb (Create) and resource (Todoist task), and the service name is a real discriminator against near-identical siblings such as todo_create_task, create_omnifocus_task, and create_reminder. It stops short of explicitly routing the agent away from those siblings, so it is clear but not fully differentiated.

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 only enumerates optional fields; it never says when to use this over todo_create_task, create_reminder, or create_omnifocus_task, nor does it state preconditions (e.g. Todoist must be connected, project must exist). No when-not guidance at all.

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