env_facts

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

Annotations already declare destructiveHint=true, so the safety profile is partly covered, and the description sensibly adds that secrets must not go here. But it never says whether an 'add' overwrites an existing key, whether facts persist across sessions, or what 'auto-detected' project resolution means in practice, which matters for a write-capable tool.

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?

Two sentences, front-loaded with the core capability and immediately followed by the exclusion rule. No filler, no restatement of the name, every clause carries information.

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 6-parameter, write-capable tool with no output schema, the description covers the what and the secrets boundary but omits return/listing behavior and the semantics of repeated adds. Adequate to call correctly, but not complete.

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 100%, so key, value, context, project, workspace_path, and the action enum are all documented in the schema itself. The description only reinforces the value domain (auth backend, env vars, URLs) without adding format, validation, or defaulting detail, so it meets the baseline but not more.

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 specific verbs (store and query) applied to a specific resource (stable environment facts for a project), and the parenthetical examples (auth backend, env file locations, local URLs, required env vars) make the scope concrete. It also names the adjacent-but-different sibling cred_refs so the agent can separate the two without reading schemas.

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?

Explicitly carves out the boundary case: 'Not for secrets — use cred_refs for that.' That is a genuine when-not rule with a named alternative. It does not, however, describe when to prefer env_facts over project_context, learn, or register, some of which store project-level knowledge, leaving the broader routing implicit.

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