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

With no annotations, the description carries the full behavioral burden and does well: it explains omit-to-keep semantics, the replace/clear/keep behaviour of the zone lists, that header/footer are global blocks edited elsewhere, and that a contract doc governs the operation. It does not cover failure modes, permissions, or reversibility, so it stops short of exhaustive.

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 create/update purpose, followed by the dedupe instruction and the global-block workflow, then a final rule line. Dense but each sentence earns its place for an 8-parameter tool with nested objects; only the density slightly taxes readability.

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, 8-param nested-object mutation with an output schema (so return values need not be explained), the description covers the purpose, the omit-to-keep contract, the required prerequisite doc, and the header/footer global-block dependency. What remains thin is error/permission behaviour, but the operational essentials are present.

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 schema already documents every parameter (templateId, headerPatternId, beforeSlot/afterSlot, contentSource rules, etc.). The description mostly restates the create/update and global-block wiring rather than adding format or syntax details beyond the schema, which is the expected baseline when coverage is complete.

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 pair (Create / UPDATE) on a clearly defined resource ('a site template — a header+footer frame around pages'), and explicitly tells the agent when it is a create vs an update via templateId. It also routes the reader to the relevant siblings (list-templates, save-synced-pattern), so it is distinguishable without opening any 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 explicit when-to-use guidance: 'Check list-templates first: edit the existing one rather than make a duplicate,' plus a hard prerequisite ('read [template-contract] before the first call') and the correct alternative path for building the header (list-synced-patterns / save-synced-pattern). Nothing about selecting this tool over alternatives is left implicit.

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