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

Annotations give the safety profile (readOnly=false, destructive=false, idempotent=false), and the description adds substantial context beyond them: re-call safety with existing entries preserved, autonomous self-writing at the site's cadence, and the 'held' behavior returning status 'queued' with kind 'research'. This is exactly the behavioral detail an agent needs and cannot get from the structured fields.

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?

Front-loaded with the primary action, then the idempotency note, then the async/held branch, then the alternative tool. Sentences are dense but each earns its place. Slightly long, but no wasted 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?

No output schema exists, and the description compensates by specifying the return shape ('status "queued"' with 'kind "research"') and the side effects (scheduled entries write themselves). It also names the sibling it is not. Nothing critical for correct invocation is missing.

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% (both site and horizonWeeks are documented with enum values), so the schema carries the parameter burden. The description mentions the 'planning horizon' which loosely maps to horizonWeeks but adds no syntax or constraint detail beyond the schema. Baseline 3 is appropriate.

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 opens with a specific verb+resource ('Generate the content plan, or refill the open slots in the planning horizon from the site's keyword research'), clearly distinguishing this from siblings like get_plan, add_to_plan, and update_plan_entry. An agent can identify the operation without inspecting 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 explicitly routes the agent to an alternative ('Use add_to_plan to add one specific keyword instead') and describes the exact recovery flow when research is still running (poll with get_job, then call generate_plan again). When-to-use and what-to-do-instead are both covered.

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