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

With no annotations, the description carries full burden. It discloses that the tool is 'Free and owner-scoped', explains update behavior (fields only change if passed, favorite null keeps as-is), and mentions the return format. The doc field is described as 'same block/flag document a post carries'. This provides sufficient behavioral context for an agent.

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 description is three well-organized sentences: first sentence states purpose and create/update distinction, second details update behavior, third clarifies doc and scope. No wasted words; front-loaded with key action.

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?

Given 7 parameters, no annotations, and an output schema, the description covers the core logic, update rules, scope, and return type. It mentions doc parity with posts, aiding context. The only minor gap is dpop_token meaning, but that is likely standard across tools. Overall, it's nearly complete for safe agent invocation.

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 only 14% (only npub has a description). The description adds critical semantics for snippet_id (omit to create, pass to update) and favorite (null to keep as-is), and notes doc is identical to post. However, dpop_token, name, and text lack elaboration, partially compensating but not fully covering all params.

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 clearly states 'Save a reusable post snippet (opening/footer/CTA)' and explicitly distinguishes creation (omit snippet_id) from update (pass it). Among siblings like excalibur_create_post and excalibur_get_snippet, this tool is uniquely for snippets with both create and update capabilities, making its purpose well-defined.

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?

The description provides explicit guidance: omit snippet_id to create, pass it to update, and notes that on update only passed fields change with special handling for favorite. While it doesn't explicitly state when to avoid using this tool, the context and siblings imply its scope is for snippet management, which is clear.

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