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

With no annotations, the description carries the transparency burden. It discloses accepted input formats, the diff logic (added, removed, lastmod-changed), the filtering to relevant URLs, and the optional key-driven POST body. This is sufficient for a read-only analysis tool.

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 exactly two sentences, front-loaded with the main verb and object, and every clause adds value. No filler or repetition of schema details.

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 moderate complexity (6 params, no output schema), the description adequately covers inputs, processing, and output categories. It doesn't specify the exact return format, but the phrase 'reports added, removed and lastmod-changed URLs' gives enough guidance for an agent to interpret results.

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 baseline is 3. The description adds meaning beyond the schema by specifying the document formats for previous_sitemap/current_sitemap and explaining that the key can yield a 'finished, validated POST body.' This adds useful context to the parameters.

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 the specific action: 'Parses two sitemap documents' and 'reports added, removed and lastmod-changed URLs.' It also names the output scope ('URLs worth submitting to IndexNow'), distinguishing this tool from siblings that build or validate messages.

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 makes the primary use case explicit: diff two sitemaps to produce a submission list. It doesn't explicitly mention when to choose build_indexnow_payload or validate_indexnow_key, but the context implies the workflow, so there's no exclusion gap.

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