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

The description clearly discloses the destructive/overwrite behavior: 'Replacement fields overwrite previous values.' It adds permission requirements and the persona overlap warning, which go beyond what annotations already signal. There is no contradiction with the provided readOnlyHint=false and destructiveHint=true 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?

The description is efficiently front-loaded with the core purpose, followed by warnings, permissions, alternatives, and ID format. Every sentence earns its place despite the tool having 10 parameters and a destructive nature.

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, destructive update tool with no output schema, this description is exceptionally complete. It covers purpose, overlap with siblings, permission requirements, overwrite semantics, and target ID format. The agent has all necessary context to select and safely invoke the tool.

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 schema has 100% parameter coverage, giving the baseline of 3. The description adds valuable semantics beyond the schema by explaining that fields are replacements, specifying playbook_id must be UUID or GUID, and clarifying the distinction between instructions and persona fields. This meaningfully helps an agent pass parameters correctly.

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 opens with a precise verb and resource ('Update this playbook's name, description, visibility, tags, config, singleton persona fields, or always-on project instructions'), which makes the tool's scope immediately clear. It also differentiates this from sibling tools by explicitly noting overlap with update_persona and create_persona.

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?

The description gives explicit guidance on when NOT to use this tool: 'use those when only the persona should change.' It also clarifies how to read persona data via get_playbook, which prevents misuse. The permission requirement ('Requires full or playbooks:write permission') and caution ('Handle with extreme care') add practical usage context.

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