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

While annotations already mark readOnly=true and idempotent=true, the description adds non-obvious behaviors: the GDELT→GNews fallback on rate limit/5xx, USPTO soft-fail due to PatentsView sunset, and accepted `since` formats. This transparently discloses edge-case behavior beyond annotation hints.

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 long but structured: it opens with user-intent examples, then sources/fallback, then input format, then output, then alternative. Every sentence provides distinct value with no redundancy, though slightly dense for a multi-source tool.

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 no output schema, the description compensates by specifying return structure (changes[] grouped by source, total_changes, citation URIs) and covers failure modes (soft-fail, fallback). It also disambiguates from entity_profile, making the tool contextually complete for an agent.

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 already covers all 3 parameters with descriptions, so baseline 3. The description adds practical details like `since` relative shorthand examples ('7d', '30d', '3m', '1y') and `value` as ticker or zero-padded CIK, which aids correct invocation beyond the schema.

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 explicitly states the tool is a 'change feed for a company' and provides concrete user intents ('What's new with X', 'latest on Y'). It names the verb 'fans out' and lists specific sources (SEC EDGAR, GDELT/GNews, USPTO), clearly distinguishing it from entity_profile.

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 usage context through query paraphrases and states a clear alternative: 'Use entity_profile instead when you want the static profile (filings + fundamentals + LEI + patents) regardless of window.' This gives unambiguous when-to-use and when-not-to-use guidance.

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