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

With no annotations, the description carries the full behavioral burden and does so richly: it discloses partial-update semantics (only what you pass is touched), an authorization constraint (only the attacher and project lead may edit), REPLACES vs empties behavior for the reader list, and that the response never contains the value. It even warns against leaking the secret into other text.

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 id source are front-loaded, and nearly every sentence adds operational or safety value. It is denser than strictly necessary in places, but no sentence is wasted.

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 mutation tool with no annotations and no output schema, the description covers authorization, partial-update behavior, list-replacement semantics, and the return/security posture ('the answer never carries the value'). Nothing an agent needs to call it safely and 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 is 3, but the description adds value beyond the schema by explaining the 'readers' replace-vs-keep distinction and that removing a reader never requires the value. These are semantic insights the schema states only partially.

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+resource ("Change a credential") and enumerates exactly what is mutable (name, value, readers), while pointing to list_credentials for the id. An agent can distinguish this from create_credential/delete_credential/reveal_credential by the nature of the operation described.

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 clear operating context: use the id from list_credentials, and pass only the fields to change since untouched fields are preserved. It implies but never explicitly contrasts with add/delete/reveal alternatives, so it stops short of full when/when-not routing.

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