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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds value beyond them by disclosing the return shape (open and done items, each with item_id), which matters since there is no output schema. Missing details are minor: nothing on behavior for an invalid or missing plan reference beyond what the schema says.

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 tight clauses: what it reads first, when to use it second. No filler, though the phrase "shared checklist" is slightly redundant with the return-contents clause.

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?

A single-parameter read tool with no output schema; the description compensates by naming the returned fields and the user intent that should trigger it. Nothing essential to 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% and the plan parameter already documents the accepted link format and the rejected draft-link case in detail. The description adds nothing about the parameter, so the baseline 3 applies.

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 ("Reads the plan's shared checklist") and names the payload contents (open and done items with item_id), so an agent knows exactly what it returns. Sibling differentiation is only implicit — it never names check_item or get_plan — but the read-only framing makes the split from mutation siblings clear enough.

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 sentence "Use when the user asks what still needs doing or what is on the list" gives a concrete triggering condition. It offers no explicit exclusions or named alternatives (e.g. check_item for marking items done), so it stops short of the 5 bar.

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