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

Annotations already establish the safe read-only, non-destructive, non-open-world profile. The description goes further by disclosing scan behaviour ('how many keys it examined and whether it stopped early') and the matching rules (case-sensitive, full key including prefix), which matter for predicting results. It does not cover rate limits or the failure mode when both glob and regex are omitted.

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?

Purpose and the mutual-exclusion rule are front-loaded, and each subsequent sentence carries concrete, non-redundant matching detail. Six sentences is on the long side, though the density is justified by the glob-versus-regex subtlety.

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?

There is no output schema, and the description compensates by stating what the response reports (keys examined, early stop). With all six parameters schema-documented and the matching semantics fully spelled out, nothing an agent needs to call this 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 coverage is 100%, so the baseline would be 3, but the description adds substantial meaning: glob must match the WHOLE key ('invoice' matches nothing while '*invoice*' works), '*' crosses '/' boundaries, '?' matches one character, and regex is searched anywhere in the key. This is exactly the semantics an agent needs and the schema terse descriptions do not supply.

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 (finds) and resource (objects) and immediately scopes it: 'at any depth under a prefix whose key matches a pattern'. It explicitly contrasts with the sibling behaviour of 'listing folders one level at a time', so an agent can distinguish it from list_objects without opening either 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 a hard usage rule ('Pass exactly one of glob or regex') and explains the trade-off between the two modes, which is effectively guidance on which parameter to pick. It does not name list_objects as the alternative to avoid, so the routing is implied rather than explicit.

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