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

Annotations already flag destructiveHint=true and readOnlyHint=false, and the description adds genuinely new behavior: values are encrypted at rest and not echoed back, and the operation merges rather than replaces. It does not state that an existing key's value is overwritten by a set, which is the main remaining gap given destructiveHint=true. No contradiction with annotations.

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?

A single tight sentence with the operation front-loaded and the security caveat in a parenthetical - no wasted words. It is arguably too terse for a destructive mutation, but nothing in it is filler.

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?

With no output schema and only two parameters, the description covers the essentials, but for a destructive write tool it omits overwrite semantics, whether a project must be active (session vs project_id), and any confirmation/irreversibility note. Adequate but with clear gaps for a mutation.

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 50%: project_id is documented in-schema, but the vars array and its key/value items have no descriptions anywhere. The description's note that values are encrypted and not echoed back does add meaning for the 'value' field, but it says nothing about key naming rules, duplicate keys, or how merge conflicts resolve.

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 pair (set/merge) and resource (project secrets / env vars), which goes beyond the bare title. It is clear what the tool does, but it never names its read-side sibling list_env_keys or otherwise differentiates itself from the other project-mutation tools.

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?

'Set/merge' implies additive behavior (existing keys are retained rather than wiped), which is a usage-relevant signal. However, there is no explicit when-to-use/what-not-to-do guidance and no pointer to list_env_keys for inspection before writing; the agent must infer context.

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