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

Annotations already declare non-destructive, idempotent, closed-world behavior; the description adds genuinely new context beyond them: duplicate names return the existing sphere rather than creating a twin, and the free plan caps Planning spheres at 3 while Goals/Focus spheres are free. It omits permission requirements and what the returned object looks like, so not a 5.

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 section meanings are front-loaded and each sentence carries information (trigger, defaults, dedupe, quota). The dedupe sentence is slightly convoluted ('returned instead of a twin') and the quota sentence could be tighter.

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 no output schema, the description reasonably covers the important return behavior (existing sphere returned on name collision) and the plan limits that affect success. It doesn't describe the created sphere's shape or what happens if the 3-sphere cap is exceeded, leaving a small gap for a mutation tool.

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 67% and the description supplies the one significant missing semantic: 'Planning by default' for the sections parameter, plus the mapping of each section to its surface (planning=tasks, goals=Goals canvas, focus=Focus points, visualisations). It says nothing about the color parameter, which is only documented in the 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?

States a specific verb+resource ('Create a sphere') and glosses the domain term as '(life area)', then enumerates the sections it can live in. An agent can distinguish this from list_spheres/update_sphere/archive_sphere 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?

Gives an explicit trigger ('when the user asks for a new area') and notes the dedupe behavior when a same-named sphere already exists. It does not name a concrete alternative (e.g., use update_sphere to add a section to an existing sphere), so it stops short of full routing guidance.

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