fill_secret

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

With no annotations, the description carries the behavioral burden well: it discloses that the vault types the value so the agent never sees it (a critical privacy trait), and that filling is constrained to saved sites and matching field kinds. It omits failure/error behavior and what happens when no matching item exists, keeping it from a 5.

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 purpose, key constraint (agent never sees the value), and fill-matching rule are all front-loaded before the parameter notes. Sentences are tight and each carries information, though the trailing param block reads slightly like an appended glossary.

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 restated, and the description covers the fill semantics thoroughly for a 3-param tool with no annotations. The remaining gap is error/edge behavior (item not found, selector mismatch) for what is effectively a mutation of form state.

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 0%, so the description must compensate, and it does: selector is explained as the target field with an example, name is tied to the sibling list_secrets as its source, and field enumerates the valid values (username, password, totp). This is meaningful semantics well beyond the schema's bare titles.

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 opening sentence states a specific verb and resource (fill a field from the password manager) and immediately distinguishes itself from the sibling type_text by noting the vault enters the value rather than the agent. An agent can tell exactly what this tool does without opening the 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?

It gives clear conditions for correct use (site must be saved with the item, field type must match) and describes the follow-up action (click the sign-in button as usual, i.e. use the click sibling). It does not explicitly name type_text as the alternative for non-secret text, so it stops short of full when-not routing.

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