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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds useful context beyond that: which ownership classes of templates appear in the result and the fact that only the user's own are editable. It does not mention result ordering or result volume, which is a minor gap.

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 tight sentences: what is returned first, then what to do with the results. No filler or restated name/title, and the actionable routing is front-loaded in the second sentence.

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 no-required-param, three-optional-filter list tool with full schema coverage and annotations, the description covers scope and follow-up actions adequately. It leaves return shape (fields per template, ordering, pagination) unstated, though no output schema exists to compensate.

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% with per-parameter descriptions and a size enum, so the schema carries the parameter burden. The description only alludes to the gallery parameter through the phrase 'Spur's built-in gallery' and adds no filter semantics beyond that, so the baseline 3 applies.

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 the specific resource (postcard templates) and enumerates the three scopes returned: user's own editable templates, Spur defaults, and the built-in gallery. An agent can distinguish this from spur_list_letter_templates or spur_list_images purely from the text.

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?

Explicitly routes next steps: copy a default/gallery design via spur_create_postcard_template with base_template_id, or start blank with start_from_blank. It does not say when to avoid this tool (e.g., when fetching a single template by id, which is spur_get_postcard_template), so it stops short of full when/when-not guidance.

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