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

With readOnlyHint=false and destructiveHint=true already signaling mutation, the description adds concrete behavioral context: the upsert semantics, the exact fields changed on update, and that it returns the saved list. It doesn't cover permission requirements, but annotations already carry the safety signal.

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 sentences with no filler. The core behavior is front-loaded, followed by the create/update distinction and return value; every sentence earns its place.

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 moderately simple upsert tool with fully documented parameters, a descriptive output schema, and annotations covering the destructive nature, the description supplies the missing operational semantics (how to choose create vs update). Nothing essential 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%, so the baseline applies. The description restates the conditional relationship between omitting id and requiring name, but this is already present in the parameter descriptions; it doesn't add new parameter-level meaning beyond 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?

Description opens with the verb 'Upsert' and the resource 'list', then details the two modes: create without id and update with id (rename/change emoji). This clearly separates save_list from sibling tools like save_task and view_lists.

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 explicitly tells an agent when to create (omit id) versus update (pass id), which is the key routing decision. It doesn't name siblings like view_lists as alternatives for read-only access, so it stops short of full exclusion guidance.

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