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

Beyond the readOnly/idempotent/non-destructive annotations, the description discloses a real behavioral caveat: 'many notes are not tagged with a context,' warning the agent that context filtering is unreliable. It also enumerates the returned content (contexts plus counts, active context ids, earliest/latest dates), which is exactly the kind of context annotations cannot carry.

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?

Front-loaded with the discovery purpose, then the return payload, then the calling rule and the caveat—every sentence earns its place with no filler or repetition. It stays compact despite covering return shape and usage guidance.

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 fills the gap by detailing what the call returns and when to use it, so an agent needs nothing further to call it correctly. The data-sparsity note closes the remaining risk of over-relying on context filters.

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?

The tool takes no input parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description does not need to compensate for any schema gap.

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?

Names a specific verb+resource ('List Contexts and Filters') and defines what 'contexts' actually are (modes with id, prompt, icon, color) plus the filter facets returned. It is clearly distinguishable from siblings like list_labels and filter_notes_by_label because it explicitly describes the discovery role.

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 ordering rule ('Call this FIRST when the user asks to filter notes by a context or by date') and states the payoff ('so you use valid ids and a valid date range'). It also steers away from the wrong approach by recommending text search and dates as primary filters.

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