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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the write operation is implied. The description adds non-obvious behavioral context: the default list is idempotent and named 'Favoritos', which is valuable beyond the raw schema.

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 short sentences, no filler, and the trigger condition is front-loaded. Every phrase earns its place and the default-list rule is clearly stated.

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 simple 4-parameter write action with an output schema and annotations, the description covers the key decision rule (default list fallback) and user context. It could elaborate on listId vs listName precedence, but the schema already documents these fields.

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 is 3. The description adds meaning by explaining that when listId/listName are not supplied, the idempotent 'Favoritos' list is used, which clarifies the optional list parameters beyond the schema defaults.

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 clearly states the verb 'save' applied to a property and the target 'favorite list', which directly distinguishes it from siblings like remove_property_from_list and get_property_list. It also mentions the default list behavior, making the tool's purpose unambiguous.

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 says 'Use this when an authenticated user asks to save a property to a favorite list' and provides the fallback rule for when no list is supplied. It does not explicitly name alternatives such as remove_property_from_list for removals, so it stops short of a 5.

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