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

Annotations already declare readOnlyHint=false, openWorldHint=false, and destructiveHint=false, but the description adds substantial behavioral context: events appear as chart annotations, widget definitions create visual annotations, widget is a full replacement on update, source is server-set, deprecated aliases are ignored, and list_tags should be used before creating tags. No annotation contradiction.

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?

The description is long but well-structured and front-loads the purpose and primary usage guidance before parameter details and the example. The example is useful for a nested widget object, though some widget and metadata guidance is repeated from the schema.

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 complex create tool with nine parameters, nested widget objects, and no output schema, the description is thorough about creation semantics, annotation behavior, tag discovery, metadata handling, and example usage. It does not describe the return value, error behavior, or permission requirements, but those gaps are relatively minor given the schema coverage.

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 goes beyond the schema by emphasizing that widget is STRONGLY RECOMMENDED, explaining when to omit it, noting that null is equivalent to omit for scopeId on create, and providing a complete example invocation. Some of this overlaps with schema descriptions, but it meaningfully improves parameter understanding.

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 and resource: 'Create a new event to annotate a cost change.' It explains the event's role as a chart annotation, which distinguishes this create/annotation tool from list_events and update_event without opening either 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 clear when-to-use context ('when the user wants to document why costs changed') and instructions for the widget parameter, including when to omit it. It also points to list_tags before inventing new tag values. It does not explicitly say when to use update_event instead for existing events, so it falls short of full alternative routing.

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