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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds a workflow-oriented behavioral note about preferring replacements for small edits, which is useful. It does not describe authentication, rate limits, or return-format details beyond what annotations already imply.

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 sentences, both front-loaded and purposeful. The primary operation is stated first, followed by a concise alternative-usage rule. There is no redundant or filler language.

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 two-parameter getter with full schema coverage and clear annotations, the description is largely complete. It explains the core action and one important alternative workflow. It could mention that the result is HTML content specifically, but the title and description already imply this.

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 both parameters are already documented in the schema. The description does not add syntax, defaults, or enum meaning beyond what the schema provides. Baseline 3 is appropriate when the schema fully carries parameter semantics.

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 uses a specific verb and resource: 'Fetch a postcard template's HTML.' It clearly distinguishes the core operation from sibling update tools by naming spur_update_postcard_template. It does not explicitly distinguish from preview or list siblings, but the purpose is still clear.

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 gives a concrete usage rule: for small text changes, prefer spur_update_postcard_template with replacements instead of resending whole HTML. This names the alternative and the condition for choosing it. It lacks guidance on when to use this versus preview_postcard_template or list_postcard_templates.

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