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

Annotations already declare non-read-only, idempotent, non-destructive, but the description adds substantive behavior: only passed fields change, images are stored by URL so deleting the file breaks them, template content is immutable, admin gating for public templates, and an access-model caveat with a reference link. This is well beyond annotation coverage.

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-loads the mutation scope in sentence one, then groups image workflow, immutability, and access rules. Dense but every clause carries information; slightly run-on with parentheticals and a reference path embedded mid-prose.

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 still says the return mirrors riddle_template_create, and it covers the access model, image lifecycle caveat, and field-level mutation semantics for a 5-parameter mutation tool. Nothing essential to correct invocation is missing.

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 baseline is 3, but the description adds real meaning the schema lacks: it ties coverMediaId/iconMediaId to a media_upload_link workflow, clarifies that passing only some fields mutates only those fields, and explains the remove fallback semantics (cover to the Riddle's cover, icon to the type default).

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 ('Changes') and resource ('a template') plus the exact mutable fields (title, gallery image, icon). It is clearly distinguishable from riddle_template_create, riddle_template_get and riddle_rename, which handle other operations on the same domain.

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 real prerequisites: images must first go through media_upload_link into the template's project and the reported mediaId must be passed; public templates are admin-only; without full access the Riddle must have origin.writableByThisKey true. It also implies the alternative (create a new template from an edited Riddle), though it never frames this as an explicit when-to-use-this-vs-that rule.

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