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

Beyond the annotations (readOnly=false, idempotent=false, destructive=false, openWorld=false), the description discloses the actual mechanics not captured anywhere else: presigned PUT URLs, the mandatory client PUT step, the batch confirm step, atomic batch creation, and per-plan file caps. It omits URL expiry/rate-limit details, but the workflow disclosure is substantial.

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-loaded with purpose and the inline-limit justification before the conditional parameters and workflow. It is a dense four-sentence block with no filler, though the plan-cap enumeration is verbose relative to its decision value.

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?

An output schema exists, so return values need no explanation, and the description still covers the full call lifecycle (reserve → PUT → confirm), plan limits, and the new-site vs existing-site branches. Nothing an agent needs to invoke it correctly 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 description coverage is 100%, so the schema already documents site_id/subdomain/title/mode semantics including the merge-vs-replace distinction and the 'only used with site_id' conditionals. The description restates the site_id create-vs-add behavior but adds little the schema does not already carry, so 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 a specific verb and resource — 'Reserve presigned PUT URLs for uploading one or more large or binary files directly to storage' — and immediately scopes it against the inline path with 'bypassing the 1 MB inline limit.' This lets an agent distinguish it from write_site_files and confirm_upload without opening any schema.

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 clear conditional routing: 'Omit site_id to create a new pending site atomically' versus 'Provide site_id to add or replace files on an existing site,' plus the required follow-up sequence (PUT each file, then call confirm_upload once). It does not explicitly compare itself to siblings like write_site_files or replace_site_files, so it stops short of full when-not guidance.

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