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

Beyond the annotations (non-read-only, non-destructive, non-idempotent, closed-world), the description discloses the draft lifecycle, the requirement of explicit user approval before validation, the 200-step ceiling, the free-tier limit of one open plan, and the server-side refusal conditions (card numbers, API/private keys, passwords). That is substantial behavioral context an agent cannot derive 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?

Purpose and usage are front-loaded, parameters follow as scannable bullets, and behavioral constraints close the block. Despite its length, every sentence adds a constraint or a routing instruction, so nothing is padding.

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?

For a write tool with no output schema and only safety-oriented annotations, the description covers creation semantics, the draft/approval workflow, hard limits, and failure modes. The only minor omission is the shape of the returned plan identifier, which is implied by the instruction to pass it to plan_validate.

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 0%, so the description carries the full burden, and it does: project (with a pointer to project_list), goal, and phases are all defined, plus the nested shape of phases (ordered titles/steps) and steps (title, instruction, checklist of 1-6 verifiable criteria, deliverable). This meaningfully compensates for the undocumented schema.

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 and resource ('Creates a step-by-step plan as a draft, attached to one of the user's projects') and frames the artifact's lifecycle, which cleanly separates it from siblings like plan_list, plan_status, and plan_validate. An agent can identify the tool without opening 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 states when to use it ('when the user wants to reach a goal through ordered phases and steps, and to follow it from one conversation or assistant to another') and routes the agent to the sibling plan_validate only after explicit user approval. There is no explicit when-not guidance against alternatives such as plan_propose_amendment, so it falls just short of the top band.

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