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

Annotations already declare readOnlyHint, idempotentHint, so 'Read-only' in the description is redundant. The description does add useful behavioral content (what is returned: required/optional fields, shapes, allowed values, rules, examples), but it also describes a refusal path tied to assistant_name/save_as_default, parameters this tool cannot accept, which is misleading behavior disclosure.

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 first sentence is well front-loaded and precise. The remaining sentences drift into assistant-naming and default-saving rules that belong to a different tool, so several sentences do not earn their place in this definition.

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?

There is no output schema, so the description carries the burden of previewing the return value; it does list the categories returned (fields, rules, examples) but gives no sense of structure, size, or format. It is adequate for a zero-parameter read-only documentation tool, but the embedded non-existent-parameter guidance muddies the picture.

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 zero parameters with additionalProperties=false, so there is no real parameter surface to document. The description instead discusses assistant_name and save_as_default as if they were options of this call, which conflicts with the empty, closed schema and could lead an agent to pass arguments that will be rejected. Nothing of value is added about actual inputs.

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 and resource (returns the Errands brief fields, rules, and worked examples) and even enumerates the categories of content returned, so the agent knows exactly what this tool yields. It does not, however, distinguish itself from the many other describe/get siblings beyond naming set_assistant_name in passing.

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?

Usage is only implied: the agent is expected to infer that this is the way to learn the Errands brief before building one. The one explicit when-to-use statement ('set it with set_assistant_name') concerns a parameter that does not exist on this tool, so it does not give usable routing guidance for describe_errand_template itself.

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