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

Annotations already indicate it's not read-only and not destructive. The description adds crucial behavioral details: fails with conflict once decision is settled, may return needs_confirmation, and repeatWeeklyUntil writes one row per week (max 60), each movable. This goes beyond what annotations provide.

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 core action and immediately addresses entryId. The description is dense but well-structured, covering multiple scenarios efficiently. It could be slightly more concise, but every sentence adds necessary context for a tool with 13 parameters.

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?

Given 13 parameters, no output schema, and annotations that only cover safety hints, the description does a good job explaining key behaviors, failure modes, and parameter usage. It doesn't cover all parameters (e.g., workspace, tags), but those are documented in the schema. It's nearly complete for an agent to call correctly.

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 85%, so baseline is 3. The description adds value by explaining entryId's purpose ('the work that carries it out'), when to omit it ('standalone date'), the all-day vs timed distinction (startTime/timeZone/endTime), and repeatWeeklyUntil's weekly row behavior (max 60). Some parameters like workspace are not covered, but the description enhances understanding of key parameters.

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+resource: 'Adds a plan item to an OPEN decision'. It also clarifies the conceptual model (plan item = work that carries out a decision) and distinguishes from the sibling ledger_entries_create by describing when to use which. An agent can immediately understand this adds a dated work item, not a decision or evidence.

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?

Explicitly states when to use entryId vs omit it (standalone dates), when to use all-day vs timed, and when to redirect to ledger_entries_create instead. However, it doesn't mention ledger_plan_update or ledger_plan_delete as alternatives for editing/removing items, though those siblings exist.

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