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

Annotations already declare readOnly, idempotent, non-destructive, so safety is covered. The description adds useful scope context (three template sources, two letter-type categories), but says nothing about return format, ordering, or volume. It also references a 'start_from_blank' token that is not a parameter here, which slightly muddies rather than clarifies behavior.

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, purpose front-loaded, no filler. The first sentence is grammatically awkward (colon-delimited list fragment) but still parsable and compact.

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?

With no output schema, the description does describe what comes back (templates annotated with letter type and their source group), which is the key missing piece for an agent. It omits any mention of the category filter or result size/ordering, so it is good but not fully complete.

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 coverage is 100%, so the schema already documents category, letter_type, and include_gallery. The description restates the letter-type values in human form (Top First Page / Insert Blank Page) and alludes to the gallery toggle, but adds no filtering syntax, precedence, or default behavior beyond the schema. Baseline 3 is appropriate.

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?

It clearly states this returns letter templates for the user and names the three sources (own/editable, Spur defaults, built-in gallery) plus the letter-type dimension, which distinguishes it from siblings like spur_get_letter_template (single item) and spur_list_message_templates (different resource). The lead is a noun phrase rather than a verb, but the resource and scope are unambiguous.

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 concrete next-step guidance: copy a listed template via spur_create_letter_template with base_template_id to redesign, or start from blank. That tells the agent how this list feeds a follow-up action. It stops short of explicitly excluding alternatives (e.g., when to use get vs list), so it is clear context without full exclusions.

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