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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, and the description reinforces read-only behavior. It adds value beyond annotations by disclosing the result cap (up to 8) and result shape (id, title, URL, excerpt, relevance score) plus the public-only data boundary.

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 READ ONLY and the core action, then scope, then usage and return shape. The long topical enumeration is justified as scope definition, though it could be trimmed slightly without losing meaning.

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 not be explained, yet the description still summarizes them. Combined with annotations covering safety/idempotency and the stated public-only boundary, an agent has everything needed to select and call this tool correctly.

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 both parameters are already documented with examples and the 1-8 range. The description only restates the result cap and paraphrases the query purpose, adding little semantic depth beyond the schema; 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?

Specific verb (searches) and resource (Piloxa's public Certified Mail guides) with an explicit scope of topics covered. It clearly differentiates from siblings like fetch (returns an id for fetch) and get_certified_letter_status (no person's letters are searchable).

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?

Explicitly states the use case with a worked example question and a citable-source motivation, plus a negative constraint (public pages only, no personal letters searchable). It doesn't explicitly name which sibling to use for non-public/letter lookups, but the boundary is strongly implied.

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