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

Annotations only cover the safety profile (non-read-only, non-destructive, closed-world). The description adds genuinely non-obvious behavior: duplicate names in the same sections are deduplicated and the existing sphere returned instead of a twin, plus the free-plan quota of 3 Planning spheres versus unlimited Goals/Focus. It does not describe the returned object shape, but the added semantics clearly exceed the annotations.

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?

Three dense sentences, front-loaded with the create action and the section model. Each sentence carries new information (sections, default, dedup, quota), though the parenthetical glossary is slightly list-heavy.

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 3-parameter create tool with no output schema and only safety annotations, the description covers creation semantics, defaulting, deduplication, and quota limits. The only real omission is any hint of the returned sphere object (id, fields) an agent would need for follow-up calls.

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% (name undocumented, color and sections documented). The description supplies the section-to-purpose mapping and, more usefully, the default of 'planning' when sections is omitted, which is not encoded in the schema. The 'name' constraint (1-40 chars) is left to the schema, which is acceptable.

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?

Specific verb (Create) plus resource (sphere, defined as a 'life area'), with an explicit enumeration of the sections it can live in. This clearly separates it from add_goal, add_task, and add_focus_point, which operate on other entities.

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?

'Planning by default' tells the agent the fallback section when none is supplied, and the section list gives concrete usage context. It stops short of naming when not to use it (e.g., use update_sphere to modify an existing one, list_spheres to inspect), so it is clear but not fully routing.

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