Tool Contract

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This document records the provider-visible contract for Reasonix compile-time built-in tools. It is generated from the same canonical schema path used by the runtime registry.

Tool	Read-only	Description
bash	false	Execute a command in the shell and return combined stdout/stderr. Use for builds, tests, git, package managers, etc. To search/read/list/edit/move files, prefer the dedicated tools (grep, read_file, ls, glob, edit_file, move_file) over shell grep/cat/ls/find/sed/mv/Move-Item - they behave identically on every OS. For symbol search or architecture questions, prefer LSP/read tools and targeted grep before shell commands.
bash_output	true	Read new output from a background job started with bash(run_in_background=true) or task(run_in_background=true). Returns the output produced since the last bash_output call for that job, plus its status (running/done/failed/killed). Does not block.
code_index	true	Lightweight built-in code symbol index. Prefer lsp_* for language semantics and installed code graph MCP tools for call graph, impact, and architecture relationships; use this as the local fallback for file outlines and symbol definition candidates, then verify with read_file or grep.
complete_step	true	Record the evidence-backed completion of ONE step of an approved plan. Call it as you finish each step instead of silently moving on: it signs the step off with PROOF it is done - the verification you ran (command + result), the diff/files you changed, or a manual check. A completion with no evidence is REJECTED, so don't claim a step is done until you can show why. The host advances the task list for you when you sign off - it marks this step completed and moves the next to in_progress, so you don't need a separate todo_write to mark completions. Fields: step (which step - its title or number, matching the task list), result (what is now true/changed), evidence (>=1 item, each with kind = verification|diff|files|manual and a summary, plus optional command/paths), and optional notes.
compress	true	Compress a selected part of the current model-visible conversation without deleting visible history. Use only when the user explicitly asks for context compression. Choose before to summarize everything before the uniquely matched user turn while keeping that turn and later context, or after to summarize from that turn through the last completed turn while keeping the active turn. The anchor must be an exact, unique excerpt from a real user message; use a longer excerpt if the tool reports multiple matches.
delete_range	false	Delete a contiguous text range from a file using exact start/end text anchors. Each anchor must match exactly one line. Returns unified diff on success. Use for large deletions - smaller changes should use edit_file.
delete_symbol	false	Delete a named symbol (function, method, type, interface, const, var) from a Go source file using AST parsing. For non-Go files, use delete_range with manual anchors.
edit_file	false	Replace an exact string in a file with another. old_string must occur exactly once; add surrounding context to disambiguate. Use for targeted edits instead of rewriting the whole file.
glob	true	Find files matching a glob pattern (e.g. ".go", "internal//.go", "**/.test.ts"). Supports shell metacharacters * ? [] and the recursive ** pattern.
grep	true	Search for a regular expression in a file, or recursively under a directory (skips hidden files and files matched by .gitignore). Returns matching lines as path:line:text, capped at 200 matches.
kill_shell	false	Terminate a running background job (bash or task) started with run_in_background. A no-op if the job has already finished or the id is unknown.
ls	true	List the entries of a directory. Directories are shown with a trailing slash; files show their byte size. Set recursive=true to list all nested files depth-first (skips .git/node_modules).
move_file	false	Move or rename a file from source_path to destination_path. Creates the destination parent directory as needed. Use instead of shell mv, Move-Item, or ren for file moves so workspace confinement and file-edit permissions apply.
multi_edit	false	Apply a list of edits to a single file atomically: each edit runs against the result of the previous one, all in memory; the file is rewritten only if every edit succeeds. Cheaper and safer than chaining edit_file calls - a failure in step 3 leaves the file untouched instead of half-edited.
notebook_edit	false	Edit one cell of a Jupyter notebook (.ipynb). Target a cell by 0-based cell_number (or cell_id). edit_mode: "replace" (default) swaps the cell's source; "insert" adds a new cell after cell_number (use -1 to prepend at the top), taking cell_type and new_source; "delete" removes the cell. cell_type is "code" or "markdown" (required for insert). Editing a code cell clears its outputs. Prefer this over edit_file for notebooks - it keeps the JSON valid.
read_file	true	Read a text file with optional line offset/limit. Output prefixes each line with its 1-based number so subsequent edit_file calls can target exact lines. Use offset and limit to page through large files; the tool reports total length and pagination hints in a trailer.
todo_write	true	Record and update a structured task list for the current work. Send the COMPLETE list every call - it replaces the previous one. Use it to plan multi-step work and show progress: keep exactly one item in_progress at a time, and flip an item to completed the moment it's done (don't batch completions). Skip it for trivial single-step tasks.
update_goal	true	Report this turn's disposition for the active goal: continue (work is ongoing - give a concrete next_action), complete (the request is done and verification was attempted or reported unavailable), or blocked (only the user can unblock). An optional completion account may accompany complete: verified commands are reconciled against the session's real receipts, while unverified and risks are declarations the host cannot infer and do not block Light/Balanced completion. The host validates the claim against Delivery acceptance criteria and budget and decides whether to continue automatically. Outside an active goal turn the call fails closed without changing any state.
wait	true	Block until background jobs finish, then return each job's status and final output/answer. Use to collect the result of a task(run_in_background) or bash(run_in_background) before continuing. Omit job_ids to wait for every running job.
web_fetch	true	Fetch a URL over HTTPS/HTTP and return its text content. HTML pages are reduced to readable text; JSON / plain text / markdown bodies come back verbatim. Use to read documentation pages, API responses, or source files hosted somewhere the local filesystem can't reach.
write_file	false	Write content to a file at the given path (overwriting existing content). Creates parent directories as needed.

Schema Snapshot

The exact canonical schemas are intentionally tested in code rather than copied by hand here. Run:

go test ./internal/tool -run TestBuiltinToolContractDocumentation

The test checks that every registered built-in tool has a documented name, read-only flag, description row, and canonical schema generated by tool.BuiltinContractEntries.

Default Full Boot Surface

In a default full-token boot, Reasonix sends the built-in tools above plus the session, memory, skill, subagent, LSP, install, and slash-command tools below:

Every session uses this exact executor tool surface plus one stable proxy, use_capability, so optional MCP servers (including auto_start=false) can be inspected and called without changing provider-visible schemas mid-session. The host also enforces a risk-adaptive execution contract: state-changing and verification commands need acceptance criteria when the turn is closed-loop; changed work cannot finalize without post-change review, verification, and an evidence-backed complete_step sign-off; Skill/MCP require/prefer routes are gated with host-proven evidence (including read-only answers — ordinary reads never skip a required capability); and medium/high-risk mutations force structured review / security_review results via the review-only review_report tool, whose reviewed_paths must be backed by host-observed read/diff receipts.

Unified Boot Surface

Every session uses the same provider-visible core tools and the same use_capability proxy.

The two-model Planner and all task/fleet sub-agents also use use_capability (and never direct mcp__* schemas). Planner and ordinary writer-capable sub-agents may call installed or project-configured MCP without readOnlyHint; Planner leaves destructiveHint tools for the Executor, while ordinary sub-agents use the trusted MCP path (live authorization plus explicit deny only). Writer/destructive calls are still serialized and recorded as mutations for evidence, workspace leases, and closed-loop guards. Strict read-only sub-agents share the same proxy schema and Host connections but still require readOnlyHint and non-destructive at execution time. Dual-model attaches independent proxy frontends to both Planner and Executor so a capability discovered during planning remains directly callable after handoff; their ledgers/audits are isolated while Host connections are shared. A single-model session has no independent Planner.

use_capability resolution is side-effect free: action=list returns sorted configured MCP servers without starting them; action=call on a not-yet-connected server resolves to a deferred target, Plan re-checks only an explicit phase opt-out on the real target, and the server process starts only after the permission gate and PreToolUse hooks approve the call. On-demand children share the session lifetime (they outlive the starting call and exit with the session); action=inspect lists live tools for connected servers and cached schemas otherwise, never starting a process. First discovery of a server with no schema cache goes through action=call on the mcp-server: id itself: it resolves to a gated connect (permission name = the server's dedicated mcp_connect__<server> identity, so an exact rule such as deny = ["mcp_connect__github"] blocks process startup) that connects after approval and returns the live tool directory. MCP tool rules remain exact; mcp__github__* is not a tool-name glob. Installing an MCP authorizes the Planner to use its non-destructive tools; third-party servers that omit destructiveHint are treated as user-install trust. Before every connect or tools/call, the frontend re-checks the current runtime enablement, authorization, and exact Host connection identity; another project/tab's same-name shared client is rejected without process, network, or tool dispatch.

The fixed proxy's provider-visible name, description, schema, and ordering do not change when MCP inventory changes.

When the current frontend has a session reader, the same fixed proxy also lists the read-only session:tool_result capability. It pages the complete local copy of one tool result by UTF-8 byte offset without adding a top-level schema. Calls require tool_call_id; new truncation markers also provide a stable result_ref, which is required to disambiguate repeated call IDs. offset defaults to 0, limit defaults to 16KiB and is capped at 24KiB. Each response starts with result_ref, actual offset, next_offset, total_bytes, full SHA-256, and complete, followed by the raw page. The reader is bound to the current Agent session and is not inherited from a parent when a capability frontend is cloned. A restricted child that already has use_capability may read only its own results; an allowed-tools profile without the proxy is not widened.

ask, docs, explore, fleet, forget, history, install_skill, install_source, list_sessions, lsp_definition, lsp_diagnostics, lsp_hover, lsp_references, memory, parallel_tasks, read_only_skill, read_only_task, read_session, read_skill, read_subagent_result, remember, research, review, run_skill, security_review, slash_command, task.

parallel_tasks and fleet keep their combined result below the single-tool output limit by returning a fair preview and a stable Subagent reference for every persisted child. read_subagent_result pages through one referenced final answer by UTF-8 byte offset, so long parallel research remains lossless without injecting every report into the parent context at once. References are restricted to the current conversation lineage and workspace.

use_capability (action = list | inspect | call | decline) is on the provider-visible surface for every task. Host verification obligations come from real tool actions, not from preclassifying the prompt. Optional tools stay registered for host dispatch but are not expanded into the top-level provider schema; the model reaches them through use_capability without cache-breaking schema churn.

internal/boot.TestBootToolContractMatchesProviderVisibleSurface verifies the actual boot registry contract against the provider request, including read-only flags and canonical schemas.

Unified Boot Surface (every task)

Every task starts with the same lean provider-visible core: direct coding tools, background-shell lifecycle tools, and the stable capability proxy:

bash, bash_output, edit_file, kill_shell, read_file, wait, write_file, compress (when registered), and use_capability.

Optional tools (glob, grep, ls, web_fetch, MCP, skills, subagents, docs, session history, memory mutation, workflow, and so on) remain in the host registry for dispatch. The model lists, inspects, calls, or declines them via use_capability without changing the provider tool list. Task risk changes host planning, verification, and review policy, not which tools appear on the provider-visible surface. The retired connect_tool_source path is no longer registered.