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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, non-open-world), and the description reinforces with 'It reads only' rather than contradicting. It adds genuinely new behavioral context beyond annotations: the 100-post truncation limit and the `more` indicator, plus the interactive affordances (filter, read captions, edit, approve) that define what the planner surface offers.

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?

Purpose and time-zone scoping are front-loaded, and the sibling disambiguation lands early. The middle sentence enumerating in-planner actions ('open a post to read every caption, edit a caption...') is somewhat long for what it adds, but it is relevant to what opening the planner actually exposes.

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?

With an output schema and full annotation coverage, the description only needs selection guidance and behavioral caveats, both of which are present (time zone, start default, 100-post cap, `more` flag). The only gap is the unmentioned `brand` parameter, which the schema covers but the description never contextualizes.

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 both parameters are already documented, and the description only restates the `start` default and time-zone semantics. The `brand` parameter is not mentioned in the description at all, so no meaning is added 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?

States a specific verb and resource (opens the week planner) plus scope (seven days of posts in the workspace's time zone, starting from `start`, default today). It explicitly distinguishes itself from the sibling `list_posts` ('returns the same posts as data without the planner'), so an agent can route correctly without opening either 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?

Gives explicit when-to-use triggers ('when the person asks to see or plan their week, or to open the calendar or planner') and names the alternative (`list_posts`) with the condition that selects it. Nothing about tool selection is left to inference.

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