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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds the genuinely useful security-relevant disclosure that only metadata is returned and never the bearer token secret. It says nothing further about pagination or output shape, but an output schema exists to carry the return structure.

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?

One compact clause with the scope front-loaded before the enumerated token kinds and the metadata-only guarantee. Every element earns its place and nothing is padded.

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?

For a zero-parameter, read-only lister with an output schema and full annotation coverage, the description supplies everything an agent needs: what is listed, that it is project-scoped, and that secrets are withheld. Only the sibling disambiguation against fillo_list_api_keys/fillo_list_sync_tokens 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?

The tool takes zero parameters, so there is no parameter semantics to describe and the baseline of 4 applies. Nothing in the description contradicts or misrepresents the empty 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?

Specific verb (list) plus a precisely scoped resource (fcli_ credentials bound to this project), and it enumerates the token kinds (CLI logins, Zapier, n8n, agent handoffs). It is not, however, differentiated from the closely named siblings fillo_list_api_keys and fillo_list_sync_tokens, so an agent cannot tell from the description alone why it would pick this over those.

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 parenthetical enumeration implies the use case (enumerating connector/CLI credentials for this project), but there is no explicit when-to-use guidance and no exclusion of alternatives such as fillo_list_api_keys or fillo_list_sync_tokens. Usage is inferable rather than stated.

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